Synthesis of second-generation Sansalvamide A derivatives: Novel templates as potential antitumor agents

Article abstract of DOI:10.1021/jo061830j

We report the synthesis of 34 second-generation Sansalvamide A derivatives. San A derivatives have unique anticancer properties and target multiple cancers, including colon, pancreatic, breast, prostate, and melanoma. As novel templates, the derivatives d

Full text of DOI:10.1021/jo061830j

Synthesis of Second-Generation Sansalvamide A Derivatives:
Novel Templates as Potential Antitumor Agents
Rodrigo A. Rodriguez, Po-Shen Pan, Chung-Mao Pan, Suchitra Ravula, Stephanie Lapera,
Erinprit K. Singh, Thomas J. Styers, Joseph D. Brown, Julia Cajica, Emily Parry,
Katerina Otrubova, and Shelli R. McAlpine*
Department of Chemistry and Biochemistry, San Diego State UniVersity, 5500 Campanile DriVe,
San Diego, California 92182-1030
mcalpine@chemistry.sdsu.edu
ReceiVed September 4, 2006
We report the synthesis of 34 second-generation Sansalvamide A derivatives. San A derivatives have
unique anticancer properties and target multiple cancers, including colon, pancreatic, breast, prostate,
and melanoma. As novel templates, the derivatives described herein explore the role of stereochemistry,
amide bond geometry, transannular hydrogen bonding, and polarity on antitumor potency. Testing the
chemotherapeutic activity of these derivatives against multiple cancer cell lines will provide clear structural
motifs and identify conformational space that is important for cytotoxicity. The 34 compounds presented
are divided into six series, where five series involve the insertion of D-amino acids in conjunction with
four structural features at each of the five positions of the macrocycle. The sixth series involves comparison
between all L- and all D-amino acid derivatives with N-methyls placed at each position around the
macrocyclic core. The four structural features explored in conjunction with D-amino acids include N-methyl
amino acids, aromatic amino acids, polar amino acids, and hydrophobic alkyl amino acids.
Introduction
number of analogues have been made; to date, ∼46 analogues
have been reported, where 36 were reported by our laboratory.4,5
These San A derivatives have demonstrated that they are
privileged structures and exhibit potency against multiple targets
in numerous cancer cell lines. Examples of potent cytotoxicity
against pancreatic,4,6 colon,3,5,7,8 breast, prostate, and melanoma
Natural products are excellent sources of potential new drug
leads. These novel structures are important for the development
of original therapeutic leads that target new biological pathways.
Sansalvamide A (San A) is one such natural product (Figure
1). San A, which is a depsipeptide isolated from a marine fungus
(Fusarium spp.), exhibits antitumor activity.1-3 A limited
(3) Belofsky, G. N.; Jensen, P. R.; Fenical, W. Tetrahedron Lett. 1999,
40, 2913-2916.
(4) Liu, S.; Gu, W.; D., L.; Ding, X.-Z.; Ujiki, M.; Adrian, T. E.; Soff,
G. A.; Silverman, R. B. J. Med. Chem. 2005, 48, 3630-3638.
(5) Styers, T. J.; Kekec, A.; Rodriguez, R.; Brown, J. D.; Cajica, J.; Pan,
P.-S.; Parry, E.; Carroll, C. L.; Medina, I.; Corral, R.; Lapera, S.; Otrubova,
K.; Pan, C.-M.; McGuire, K. L.; McAlpine, S. R. Bioorg. Med. Chem. 2006,
14, 5625-5631.
* To whom correspondence should be addressed. Fax: 619-594-4634. Tel:
619-594-5580.
(1) Cueto, M.; Jensen, P. R.; Fenical, W. Phytochemistry 2000, 55, 223-
226.
(2) Hwang, Y.; Rowley, D.; Rhodes, D.; Gertsch, J.; Fenical, W.;
Bushman, F. Mol. Pharmacol. 1999, 55, 1049-1053.
10.1021/jo061830j CCC: $37.00 © 2007 American Chemical Society
Published on Web 02/22/2007
1980
J. Org. Chem. 2007, 72, 1980-2002

SansalVamide A as a NoVel Antitumor Template
FIGURE 1. Retrosynthetic strategy.
cancers4 clearly indicate the potential of this compound class
as a platform useful in targeting these cancers.
Syntheses and evaluation of all-peptide analogues against
colon cancer cell line HCT-116, a drug-resistant cancer cell line,
have revealed two potent derivatives.4,8,9 Previous work by our
group has shown that five first-generation derivatives are potent
against the drug-sensitive colon cancer cell line HT-29,5,7 and
two demonstrate potency against two drug-resistant colon cancer
cell lines. Further, two first-generation compounds were found
to be potent against three pancreatic cancer cell lines.6 It was
the structures of these six active compounds found in the first
generation that were used as the basis for the design of second-
generation compounds (Figure 2). Assaying a diverse set of San
A analogues against multiple cancer cell lines will provide new
structures as potential antitumor agents against individual
cancers. This is particularly important given the lack of
chemotherapeutic options for patients with pancreatic and drug-
resistant colon cancers.10-14
Herein we describe the synthesis of 34 second-generation San
A derivatives. The derivatives have been expressly designed
from the first generation’s cytotoxicity data and will provide
valuable information on how stereochemistry, amide bond
geometry, and polarity impact cytotoxicity. These second-
generation derivatives also have a lower C log P average (2.2)
than the first generation (∼2.9).15 Thus, they should show
improved ability to enter cells over the first-generation ana-
FIGURE 2. First-generation derivatives found to be cytotoxic against
drug-sensitive cancer cell lines. Note, compound D was found to be
cytotoxic against pancreatic cancers.
logues. Testing the chemotherapeutic activity of these derivatives
against multiple cancer cell lines will provide clear structural
motifs and identify conformational space that is important for
cytotoxicity in multiple cancers. The recent success of San A
derivatives targeting numerous cancers emphasizes the impor-
tance of the derivatives described within as potential new lead
structures.
(6) Ujiki, M.; Milam, B.; Ding, X.-Z.; Roginsky, A. B.; Salabat, M. R.;
Talamonti, M. S.; Bell, R. H.; Gu, W.; Silverman, R. B.; Adrian, T. E.
Biochem. Biophys. Res. Commun. 2006, 340, 1224-1228.
(7) Otrubova, K.; Styers, T. J.; Pan, P.-S.; Rodriguez, R.; McGuire,
K. L.; McAlpine, S. R. Chem. Commun. 2006, 1033-1034.
(8) Carroll, C. L.; Johnston, J. V. C.; Kekec, A.; Brown, J. D.; Parry,
E.; Cajica, J.; Medina, I.; Cook, K. M.; Corral, R.; Pan, P.-S.; McAlpine,
S. R. Org. Lett. 2005, 7, 3481-3484.
(9) Lee, Y.; Silverman, R. B. Org. Lett. 2000, 2, 3743-3746.
(10) Burris, H. A.; Moore, M. J.; Andersen, J.; Greem, M. R.; Rothenberg,
M. I.; Modiano, M. R.; Cripps, M. C.; Portenoy, R. K.; Sotorniolo, A. M.;
Tarassaoff, P.; Nelson, R.; Dorr, F. A.; Stephens, C. D.; vonHoff, D.
J. Clin. Oncol. 1997, 15, 2403-2413.
Results
Synthetic Strategy. San A is composed of four L-amino acids
and one hydroxy acid. We report here the synthesis of 34 San
A peptide analogues, involving the exchange of the hydroxy
acid in position 4 to an amino acid (Figure 1). We used a
succinct solution-phase synthesis route because of the hydro-
phobic nature of the residues. Our convergent approach,
involving two fragments (Figure 1),8 is amenable to inserting
L- and D-amino acids systematically within San A. This route
was also designed to facilitate large-scale synthesis for extensive
biological studies.
(11) Sener, S. F.; Fremgen, A.; Menck, H. R.; Winchester, D. P. J. Am.
Coll. Surg. 1999, 189, 1-7.
(12) Hunstad, D. A.; Norton, J. A. Surg. Oncol. 1995, 4, 61-74.
(13) Murr, M. M.; Sarr, M. G.; Oishi, A. J.; Heerden, J. A. CA Cancer
J. Clin. 1994, 44, 304-318.
Synthesis. Synthesis of 34 San A derivatives was completed
using amino acids shown in Figure 3 via the synthetic route
outlined in Scheme 1. Using 2-(1-H-benzotriazol-1-yl)-1,1,3-
tetramethyluronium tetrafluoroborate (TBTU) and diisopropyl-
ethylamine (DIPEA), acid-protected residues 1a-d and N-Boc-
protected residues 2a-g (Scheme 1) were coupled to give the
dipeptides 1-2-Boc (90-95% yield). Deprotection of the amine
on residue 2 using TFA gave the free amines 1-2 (∼quantitative
(14) Carethers, J. M.; Chauhan, D. P.; Fink, J. L.; Nebel, S.; Bresalier,
R. S.; Howell, S. B.; Boland, C. R. Gastroenterology 1999, 117, 123-131.
(15) The C log P values were calculated using an algorithm. The log P
value of a compound, which is the logarithm of its partition coefficient
between n-octanol and water log(coctanol/cwater), is a well established measure
of the compound’s hydrophilicity. Low hydrophilicities and therefore high
log P values cause poor absorption or permeation. It has been shown for
compounds to have a reasonable probability of being well absorb their log
P value must not be greater than 5.0. The distribution of calculated log P
values of more than 3000 drugs on the market underlines this fact.
J. Org. Chem, Vol. 72, No. 6, 2007 1981

Rodriguez et al.
FIGURE 3. Amino acids used in San A derivatives.
yields). Coupling of this dipeptide to monomers 3a-h gave the
desired tripeptides (Fragment 1) in good yields (80-95%).16
The synthesis of Fragment 2 was completed by coupling residues
4a-f to residues 5a-g to give the dipeptides 4-5-Boc (90-
95% yield). The amine was deprotected on Fragment 1 using
TFA, and the acid was deprotected in Fragment 2 using lithium
hydroxide. Fragments 1 and 2 were coupled using multiple
coupling agents8,17-19 yielding 34 examples of linear pentapep-
tides (70-90% yield).16
Cyclizing large macrocycles is usually very challenging, and
typically the yields are low. The recent discovery of high-
yielding conditions20 provided the majority of macrocycles in
good yields. Dissolving the linear pentapeptide in THF (0.05
M), addition of 2 equiv of anisole, and approximately 8 drops
of concentrated HCl per 0.3 mmol of linear pentapeptide led to
partially deprotected amine within 24 h. Four drops of concen-
trated HCl per 0.3 mmol of peptide was added. The reaction
was allowed to stir at room temperature and was then checked
after 24 h by LCMS. Typically deprotection of the acid and
amine was complete within 4 days.21 Upon completion, the
reaction was concentrated in vacuo and dried on the high-vac.
The dried, crude, free amine/free acid linear pentapeptide was
dissolved in a 2:2:1 ratio of THF/CH3CN/CH2Cl2 (0.004 M).22
DIPEA (6 equiv) and three coupling agents [2-(1H-7-azaben-
zotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate
(HATU), 3-(diethoxyphosphoryloxy)-3H-benzo[d][1,2,3]triazin-
4-one (DEPBT), and TBTU (0.7 equiv each)] were added to
the reaction to yield a clear solution. Reactions were usually
complete within 4-6 h.23 The final products were generated
after a standard workup utilizing ammonium chloride, extraction
with methylene chloride, concentration in vacuo, purification
via flash chromatography, and subsequent HPLC purification
(yields ranged from 30 to 90% depending on the substrate).24
(16) Dipeptide and tripeptide structures were confirmed using 1H NMR.
All linear pentapeptides were confirmed using LCMS and 1H NMR.
(Note: 1H NMR were taken for cyclized peptides, but due to their
complexity, they were not seen as the primary confirmation for cyclized
compounds.) See Supporting Information for spectra.
(17) Unpublished results from the Guy lab at Department of Chemical
Biology and Therapeutics, St. Jude Children’s Research Hospital, Memphis,
TN 38103, and published results from our lab show that the use of several
coupling reagents facilitates formation of the peptide bond in high yields.
(18) Bolla, M. L.; Azevedo, E. V.; Smith, J. M.; Taylor, R. E.; Ranjit,
D. K.; Segall, A. M.; McAlpine, S. R. Org. Lett. 2003, 5, 109-112.
(19) Liotta, L. A.; Medina, I.; Robinson, J. L.; Carroll, C. L.; Pan, P.-S.;
Corral, R.; Johnston, J. V. C.; Cook, K. M.; Curtis, F. A.; Sharples, G. J.;
McAlpine, S. R. Tetrahedron Lett. 2004, 45, 8447-8450.
(21) For details on the reaction conditions see Supporting Information.
(22) The dodecapeptide tends to form at cyclization concentrations greater
than 0.005 M. We found that cyclizing the linear pentapeptide at 0.004 M
led to almost exclusively the pentapeptide macrocycle as the product.
(23) It was straightforward to follow the reactions via LCMS as the
starting material double deprotected linear precursor would appear at 5.0-
5.5 min and the cyclized product would appear between 6.1-7.0 min.
(20) Styers, T. J.; Rodriguez, R.; Pan, P.-S.; McAlpine, S. R. Tetrahedron
Lett. 2006, 47, 515-517.
1982 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
SCHEME 1. Synthesis of San A Macrocyclic Derivatives
Structures of Macrocyclic Derivatives. The second genera-
tion of San A derivatives was divided into six series. These
series explore the impact of stereochemistry using D-amino acids
in conjunction with four structural features: N-methyl amino
acids, aromatic amino acids, polar amino acids, and hydrophobic
alkyl amino acids. They include derivatives with alterations at
position 1 (Figure 4), position 2 (Figure 5), position 3 (Figure
6), position 4 (Figure 7), position 5 (Figure 8), and comparison
of all D- and all L-amino acids in conjunction with N-methyl
moieties (Figure 9).
Figure 4 describes the alterations at position 1, where the
first-generation compounds are shown in gray and the second-
generation compounds reported here are shown in black.
Compound 1 was designed as a comparison to San A peptide
to determine if rigidifying the core structure using a confor-
mationally restricted hydrophobic aromatic moiety would
improve cytotoxicity. In the first generation, only compound
G demonstrated any antiproliferation activity. Compounds 2 and
3 were both designed to follow up on the cytotoxicity observed
with compound G, where aromatic D-amino acids with hydrogen-
bonding elements were utilized. As with compounds 2 and 3,
compounds 4 and 5 were designed to explore the importance
of a D-amino acid in position 1, but they also involved placement
of a D-amino acid in several other positions shown to be
important for cytotoxicity. Compound 4 contains a D-amino acid
in positions 1 and 5 as well as an N-methyl moiety in position
4. Compound 5 contains D-amino acids in positions 1, 3, and
4. The primary modifications to these structures involved three
of four structural features; in addition to inserting D-amino acids,
we included an N-methyl moiety 4, insertion of the tetrahy-
droisoquinoline as an alternative aromatic amino acid (com-
pound 1), and addition of polar aromatic D-amino acids
(compounds 2 and 3).
Figure 5 describes compounds with changes at position 2,
where the first-generation compounds are shown in gray and
the second-generation compounds reported here are shown in
black. In the first generation, compounds B and F demonstrated
the greatest antiproliferation activity of this series in position 2
(Figure 2).5 All seven second-generation compounds contained
D-amino acids in position 2 because the two active compounds
in the first generation contained D-amino acids in this position.
The difference between the two active first-generation com-
pounds is an N-methyl moiety; therefore, we designed this next
(24) The 34 macrocyclic peptides have LCMS spectra given in the
Supporting Information. In addition, 29 compounds out of 34 in the library
have each intermediate characterized via NMR and/or LCMS.
J. Org. Chem, Vol. 72, No. 6, 2007 1983

Rodriguez et al.
FIGURE 4. Compounds with changes in position 1: gray compounds are first generation (San A peptide, D, G, H); and black compounds are
second-generation compounds (1, 2, 3, 4, and 5).
FIGURE 5. Compounds with changes in position 2: gray compounds are first generation (San A peptide, B, F, and J); and black compounds are
second-generation compounds (6, 7, 8, 9, 10, 11, 12, and 13).
generation to contain a D-amino acid both with (compound 6)
and without (compound 7) an N-methyl moiety. In addition,
given that two of the five most potent compounds in the first
generation were compounds E, which contain an N-methyl
D-amino acid at position 3, and F, which has an N-methyl
D-amino acid in position 2 (Figure 2), we designed compound
1984 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
FIGURE 6. Compounds with changes in position 3: gray compounds are first generation (San A peptide, C, D, E, M, N, and O); and black
compounds are second-generation compounds (5, 8, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, and 27).
8. Compound 8 contains an N-methyl D-amino acid at positions
2 and 3, and therefore, the results from cytotoxicity assays would
indicate whether the insertions of these two amino acids had a
synergistic effect. Further, compounds B and C were also two
of the most biologically active compounds, and they contained
a D-amino acid in positions 2 and 3, respectively; therefore, we
designed compound 12. Compound 12 explores the synergistic
effect of placing D-amino acids in both positions but without
the N-methyl moieties present.
We also synthesized two derivatives containing hydroxyl
moieties at position 2 (compounds 9 and 10) in order to examine
whether a polar amino acid containing a H-bonding element at
this position would improve its cytotoxic effect. In addition,
we had noticed a trend that the conversion of a leucine to a
valine residue sometimes promoted cytotoxicity, perhaps due
to a lower overall molecular weight. Thus, we explored this
hypothesis by synthesizing derivative 10, which contains a serine
in position 2 and leucines in positions 4 and 5 (which parallels
those in the San A peptide) as well as 9, which contains a serine
in position 2 and valines in positions 4 and 5. Compound 11
was designed with the D-leucine seen in the active first-
generation compound B at position 2, as well as an ethyl side
chain replacing an isopropyl in position 3. This was designed
to explore the structural requirements for potency at both
positions 2 and 3. Finally, compound 13 involved placement
of a D-benzyl-protected serine at position 2. This derivative will
very effectively explore the impact of a hydrophobic aromatic
residue at this position. Thus, the primary modifications of these
structures involved three of the four structural features: inclusion
of D-amino acids with N-methyl moieties, the addition of
aromatic amino acids, and the insertion of polar residues into
the San A backbone at position 2.
Figure 6 describes compounds with changes at position 3,
where three of these first-generation compounds (gray: C, D,
J. Org. Chem, Vol. 72, No. 6, 2007 1985

Rodriguez et al.
FIGURE 7. Compounds with changes in position 4: gray compounds are first generation (San A peptide, P, Q, and R); and black compounds are
second-generation compounds (4, 21, 22, 23, 28, 29, 30, 31, and 32).
FIGURE 8. Compounds with changes in position 5: gray compounds are first generation (San A peptide, A, and S); and black compounds are
second-generation compounds (4, 24, 25, 26, and 33).
and E) were the most cytotoxic of the first-generation San A
series. Thus, we focused the design of our second-generation
compounds on making changes to this position. In the first
generation, compounds C and E demonstrated the greatest
antiproliferation activity against colon cancer cell lines.5 Given
that these two active compounds contained D-amino acids in
position 3 and were identical except that E contained an
N-methyl moiety combined with a D-amino acid at this position,
1986 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
FIGURE 9. Compounds with combinations of D-amino acids and N-methyl moieties: gray compounds are first generation (San A peptide, T, J,
U, V, W, M, X, A, Y, Z, AA, BB, and CC); and the only second-generation compound is shown in black (34).
we focused our attention on exploring this structural feature.
Thus, 16 of the 17 second-generation compounds that explored
the impact of position 3 contained D-amino acids in this position.
The design rationale for compounds 5, 8, 11, and 12 was
explained previously. The reason behind the synthesis of
compounds 14, 15, and 16 was to explore the impacts of a polar
moiety (serine), an aromatic moiety, and an ethyl moiety being
placed in position 3, respectively. Compounds 17, 18, 19, and
20 involve the conversion of L-leucines to L-valines in positions
2, 4, and 5 in order to reduce the molecular weight of the
molecule while maintaining the steric bulkiness of the side chain.
In addition to these changes, we also explored substitutions of
D-amino acids at position 3, where compounds 17 and 19 both
involved the substitution of an alkyl chain (isopropyl and ethyl,
respectively). Compounds 18 and 20 involved the substitution
of a polar moiety (serine) and an aromatic moiety (i.e., a benzyl-
protected serine). Three compounds (21, 22, and 23) in this
series explored alterations to positions 3 and 4. Compound 21
involved the substitution of an N-methyl D-amino acid in
position 3 and a cyclohexyl moiety in position 4, which provides
a hydrophobic element in position 4. Compound 22 contains a
D-amino acid in position 3 and a carboxybenzyl-protected lysine
in position 4, which incorporates an additional aromatic element
into the San A backbone. Compound 23 has a D-amino acid in
position 3 and a lysine in position 4, thus inserting a polar
element into the backbone.
the 5 positions were made in four San A derivatives (24, 25,
26, and 27). Because a first-generation derivative with a D-amino
acid in either the 3 or 5 position (C and S, respectively) was
potent in the cytotoxicity assays, a derivative containing both a
D-amino acid in positions 3 and 5 was synthesized, 24. An active
first-generation derivative incorporated an N-methyl at position
5 (A); therefore, we included a D-amino acid at position 3 into
25 and 26. Compound 25 contains an N-methyl L-leucine at
position 5, while compound 26 contains an N-methyl glycine.
Finally, in order to determine whether there is a synergistic
effect, compound 27 contains two features found to be
independently important in cytotoxicity: an N-methyl D-amino
acid at position 3 and a D-amino acid at position 5. In summary,
our structural modifications at position 3 involved all four
features, where the inclusion of N-methyl moieties, additional
aromatic amino acids, polar moieties, and hydrophobic moieties
provide compounds that allow us to optimize the structural
features required for potency.
On the basis of the cytotoxicity assays of the first-generation
structures, changes at position 4 appear to have a limited impact
on activity; therefore, the only compounds synthesized in this
series were made to determine whether modifications that would
improve solubility properties or allow attachment of a biotin
tag could be tolerated. Shown in Figure 7 are the nine
compounds generated in this series. The design rationale for
compounds 4, 21, 22, and 23 was explained previously. Similar
to 22, compounds 28 and 29 both contained a carboxybenzyl
(CBz)-protected lysine. While 22 contains a D-amino acid at
In addition to these three compounds that involve modifica-
tions at both the 3 and 4 positions, modifications to the 3 and
J. Org. Chem, Vol. 72, No. 6, 2007 1987

Rodriguez et al.
FIGURE 10. First- and second-generation compounds tested in colon cancer cell line HT-29 using thymidine uptake assays. All compounds were
tested in three separate assays, in triplicate each time (i.e., nine data points were taken for each percent inhibition given). Error ) (2%.
position 3, compound 28 does not, rather it contains all L-amino
acids. Thus 28 is identical to compound San A peptide with
the exception of the CBz-protected lysine. Compound 29 was
based on the cytotoxic compound D and, therefore, possesses
three D-amino acids in positions 1, 2, and 3 in addition to the
CBz-protected lysine at position 4. Removal of the CBz group
from compounds 28 and 29 affords compounds 30 and 31,
respectively, thus providing the free lysine at position 4. These
two compounds not only allow us to determine the impact of a
polar moiety at this position, but they offer a handle upon which
we can couple a biotin tag for affinity purification assays.
Finally, compound 32 possesses an N-methyl moiety at position
4. Thus, our structural modifications at position 4 involved all
four features, where the inclusion of N-methyl moieties,
additional aromatic amino acids, polar moieties, and hydropho-
bic moieties will provide compounds that will allow us to
explore the structural features required for potency.
On the basis of the cytotoxicity assays of the first-generation
structures, an N-methyl at position 5 appears to improve potency,
where compound A was one of the six most active compounds
in the first generation (Figure 2). Therefore, three of the five
second-generation compounds contain an N-methyl moiety at
position 5 (Figure 8). In addition, compound 33, which contains
a D-amino acid at position 5, demonstrates some potency.5 Thus,
three of the five compounds in this series contain D-amino acids
at position 5. The design rationale for compounds 4, 26, 24,
and 25 was explained previously. Given that both compounds
A and S both exhibit cytotoxicity, compound 33, which contains
an N-methyl D-amino acid at position 5, provides the opportunity
to explore the synergistic impact of a compound containing both
structural features. Thus, our structural modifications at position
5 focused on the inclusion of D-amino acids and N-methyl
moieties at position 5 in combination with structural elements
at other positions.
tive activity.5 Interestingly, both enantiomers in these enantio-
meric pairs (J and U, V and W, M and X, Y and Z, and AA
and BB) demonstrated the same activity. The only missing
enantiomers were those paired to A and CC. Given that A was
biologically active, the opposite enantiomer, 34, was synthesized
as part of this second generation of compounds.
Nine second-generation San A compounds were tested in the
colon cancer cell line HT-29 (Figure 10), which is the same
cancer cell line used for testing the first-generation compounds
(Figure 2).5 Comparison of San A peptide, which contains an
L-phenylalanine in position 1, to compound 1, which contains
an L-tetrahydroisoquinoline residue, shows that the insertion of
a rigid element in this position improves the percentage
inhibition from 33 to 50%. Comparison of G, which has a
D-phenylalanine at position 1, to compound 2, which contains
a D-tyrosine, shows that the addition of a hydrogen-bonding
element has improved the percentage inhibition from 51 to 64%.
These data suggest that perhaps the placement of a D-
tetrahydroquinoline residue with a hydroxyl moiety at position
1 will increase the potency of that derivative.
For position 2, first-generation compounds B and F contain
D-leucine in position 2, and both showed greater than 75%
inhibition. Replacement of the D-leucine residue with a D-
phenylalanine dramatically impacted the potency, dropping the
percent inhibition from 75 to 35%. These data suggest that the
binding pocket to which these San A derivatives bind cannot
accommodate this more extended aromatic moiety. Derivatives
with a smaller side chain may show greater potency than those
with an isobutyl. Interestingly, first-generation compounds F
and E, which contained N-methyl D-amino acids in positions 2
and 3, respectively, were both very potent (E ) 77% and F )
89%), yet a combination of these two moieties, compound 8, is
not potent (48% inhibition). It appears that a specific confor-
mational presentation is required for potency rather than having
a particular moiety in a definitive position. This hypothesis
seems reasonable given that recent studies show that a single
N-methyl D-amino acid can potentially “lock” the conformation
Given that both D-amino acids and N-methyl moieties appear
to play a key role in cytotoxicity,4 we systematically explored
the impact of these features on their biological activity in the
first generation of compounds (Figure 9). Thus, the activities
of San A peptide and 2, its enantiomer, were compared, and
both were found to have approximately the same antiprolifera-
1988 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
of a macrocycle into a distinct structure, thus allowing it to bind
to its biological target.25,26
Conclusion
San A derivatives have novel characteristics and are shown
to target numerous cancers, including chemotherapeutically
resistant colon and pancreatic cancers. As such, San A deriva-
tives represent a new class of privileged structures with potent
cytotoxic properties. Generation of the 34 structures described
here explore the possible synergistic placement of D-amino acids
in combination with four structural features (N-methyl amino
acids, multiple aromatics, polar side chains, and alterations in
the hydrophobic side chains). These compounds provide useful
structure-activity relationships in drug-resistant cancers and
highlight the key characteristics necessary for cytotoxicity.
Furthermore, these second-generation compounds focus prima-
rily on modifications demonstrated to increase potency in the
first generation, which includes the addition of D-amino acids
and N-methyl amino acids in positions 2, 3, and 5. This second
generation also has an average C log P ) 2.2 (versus 2.9 in the
first generation),15 and they incorporate four structural elements
not previously introduced in any San A analogues.27 These
derivatives explore the role of stereochemistry in potency,
examine the amide bond and transannular hydrogen-bonding
influence using NH and N-methyl amino acids, and investigate
the impact of polarity on cytotoxicity via substitution of
aromatic, hydrophobic, and hydrophilic amino acids. The
generation of these 34 second-generation compounds is a
significant step forward in developing San A as a potential new
class of drugs. Assays examining the cytotoxicity of these
compounds are currently underway and will be reported in due
course.
We had observed that first-generation compounds containing
a D-amino acid in position 3 tended to have reasonable potency
(compounds C and E). Interestingly, compounds N and O,
which contained methyl and ethyl moieties at this position, also
exhibited reasonable potency, perhaps due to the smaller side
chain in this position. To explore this concept at other positions,
compound 17 was synthesized with a D-valine at position 3
(similar to C) but also an L-valine at positions 2, 4, and 5 rather
than L-leucine. It appeared that this change was not favorable
as the percent growth inhibition dropped from 82% (compound
C) to 60% (compound 17). In addition, an N-methyl D-moiety
was placed in position 3 along with a cyclohexyl moiety
(compound 21). Comparison of the percentage inhibition
between E and 21 indicates that the cyclohexyl moiety dramati-
cally lowers the growth inhibition (from 89 to 22%, respec-
tively). Finally, comparison of the percent inhibition of C to
26 (82 versus 41%, respectively) suggests that a D-valine in
position 3 is not enough for potency, rather it also requires an
alkyl moiety in position 5. These data support the idea that in
order to achieve potency it is important for a specific confor-
mational presentation of the side chains, and these data point
to new structures that are useful for designing a third generation
of compounds.
With regards to position 4, it appears that a large hydrophobic
moiety at position 4 decreases the potency: E ) 89% inhibition,
and 21 ) 22% inhibition. Compound Q (inhibition ) 73%)
with an N-methyl at position 4 and D-amino acid at position 5
was relatively potent. Yet comparison of Q to 32 (inhibition )
72%), which contains only an N-methyl at position 4, suggests
that the D-amino acid at position 5 is not important for potency,
and it is the N-methyl at position 4 that plays a significant role.
Interestingly, 4, which is almost identical to Q except it has a
D-phenylalanine at position 1, has a much lower percent
inhibition (15%) compared to that of Q (73%). These data
indicate that a combination of selective D-amino acids, side
chains, and N-methylation is not synergistic. Instead, these
features play an individual role in the conformation of the
macrocycle. Finally, it was determined that an N-methyl leucine
in position 5 gave compound A with 77% inhibition, yet
compound 26, which contains an N-methyl glycine, only has
41% inhibition. Interestingly, compound 4, which is a combina-
tion of 32 (72% inhibition), G (51% inhibition), and S (73%
inhibition), gives a 15% inhibition! Thus, features shown to
enhance potency in individual compounds are clearly not
synergistic.
Experimental Methods
General Peptide Synthesis. All peptide coupling reactions were
carried out under argon with dry solvent, using methylene chloride
for dipeptide and tripeptide couplings and acetonitrile for pen-
tapeptide couplings. The amine (1.1 equiv) and acid (1 equiv) were
weighed into a dry flask along with 4 equiv of DIPEA and 1.1
equiv of TBTU. (Some coupling reactions would not go to
completion using only TBTU, and therefore, ∼0.25 equiv of HATU
and/or DEPBT was used. In a few cases, up to 1.1 equiv of all
three coupling reagents was used.) Anhydrous methylene chloride
was added to generate a 0.1 M solution. The solution was stirred
at room temperature, and reactions were monitored by TLC.
Reactions were run for 1 h before checking via TLC. If the reaction
was not complete, an additional 0.25 equiv was of HATU and
TBTU was added. If the reaction was complete, then workup was
done by washing with saturated ammonium chloride. (Note that if
acetonitrile was used for the reaction, methylene chloride was added
to the reaction upon workup and the resulting solution was washed
with ammonium chloride.) After back-extraction of aqueous layers
with methylene chloride, organic layers were combined, dried over
sodium sulfate, filtered, and concentrated. Flash chromatography
using a gradient of ethyl acetate/hexane gave our desired peptide.
General Amine Deprotection. Amines were deprotected using
20% TFA in methylene chloride (0.1 M) with 2 equiv of anisole.
The reactions were monitored by TLC, where the TLC sample was
first worked up in a mini-workup using DI water and methylene
chloride to remove TFA. Reactions were allowed to run for 1-2 h
and then concentrated in vacuo.
In summary, all compounds described in this paper are
currently being tested on colon cancer cell line HT-29, as well
as in six other cancer cell lines. These data are promising and
strongly support the synthesis of a third generation of com-
pounds. In addition, these initial SARs provide evidence that
specific features play a key role in impacting the conformation
of the macrocycles, which has a dramatic impact on their
potency. Further studies on how conformation affects potency
are underway and will be published in due course.
General Acid Deprotection. Acids were deprotected using ∼4
equiv of lithium hydroxide (or until pH ) ∼11) in methanol (0.1
M). The peptide was placed in a flask, along with lithium hydroxide
(25) Chatterjee, J.; Mierke, D. F.; Kessler, H. J. Am. Chem. Soc. 2006,
ASAP.
(26) Heller, M.; Sukopp, M.; Tsomaia, N.; John, M.; Mierke, D. F.; Reif,
B.; Kessler, H. J. Am. Chem. Soc. 2006, 128, 13806-13814.
(27) See Supporting Information for all compound structures shown in
the cytotoxicity assays.
J. Org. Chem, Vol. 72, No. 6, 2007 1989

Rodriguez et al.
and methanol and stirred overnight. Within 12 h, the acid was
usually deprotected. Workup of reactions involved the acidification
of the reaction solution using HCl to pH ) 1. The aqueous solution
was extracted three times with methylene chloride, and the
combined organic layer was dried, filtered, and concentrated in
vacuo.
1H), 2.1 (m, 2H), 3.2-3.4 (dd, 1H), 3.7 (s, 3H), 4.0-4.2 (br, 2H),
4.2 (m, RH), 5.0 (s, RH), 5.1 (s, RH), 5.2-5.4 (br, RH), 5.5 (m,
1H), 6.8 (d, 1H), 7.2-7.4 (m, 4H).
Tripeptide 1c-2a-3a-NH2. Tripeptide 1c-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (204 mg, 100% yield).
Macrocyclization Procedure (in situ). All pentapeptides were
acid- and amine-deprotected using concentrated HCl (8 drops per
0.3 mmol of linear pentapeptide) in THF (0.05 M). Anisole (2
equiv) was added to the reaction, and the reaction was stirred at
room temperature. The reaction typically took 4 days, but TLC
and LCMS were used to monitor the reaction every 12 h. LCMS
data typically indicated the reaction was ∼50% complete after the
first day. Addition of 4 drops of concentrated HCl per 0.3 mmol
of pentapeptide, stirring at rt overnight and checking the reaction
via LCMS usually showed ∼75% completion. On the fourth day,
verification of the presence of the free amine and free acid and
disappearance of the starting linear-protected pentapeptide permitted
workup. The reaction was concentrated in vacuo, and the crude,
dry, double deprotected peptide (free acid and free amine) was
dissolved in a minimum solution of THF/acetonitrile/methylene
chloride (2:2:1 ratio). Three coupling agents (DEPBT, HATU, and
TBTU) were used at ∼0.5-0.75 equiv each. These coupling agents
were dissolved in a calculated volume of dry 40% THF, 40%
acetonitrile, and 20% methylene chloride that would give a 0.004
M overall solution when included in the volume used for the
deprotected peptide. The coupling agents were then added to the
deprotected peptide solution. DIPEA (6 equiv or more in order to
neutralize the pH) was then added to the reaction. The coupling
agents are typically not very soluble in acetonitrile, which is why
a combination of solvents is used.
After 1 h, TLC and LCMS (where the LCMS sample was worked
up prior to injection) indicated that a product spot was developing.
The comparison Rf value in the product spot on TLC was the
protected linear pentapeptide. The reactions were always complete
after 2 h, and monitoring the starting material deprotected pen-
tapeptide via LCMS was the easiest method for determining
completion. Upon completion, the reaction was worked up by
washing with saturated ammonium chloride. After back-extraction
of aqueous layers with large quantities of methylene chloride, the
organic layers were combined, dried, filtered, and concentrated.
All macrocycles were purified by initially running a crude plug of
compound using an ethyl acetate/hexane gradient on silica gel, then
running a column on the isolated product. Finally, when necessary,
reverse phase HPLC was used for additional purification using a
gradient of acetonitrile and DI water with 0.1% TFA.
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 401 mg (2.2
mmol, 1.1 equiv) of amine 4a, 500 mg (2.0 mmol, 1.0 equiv) of
acid, 1.4 mL (8 equiv) of DIPEA, and 708 mg (2.2 mmol, 1.0 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (679 mg, 95%
1
yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
0.9-1.0 (m, 12H), 1.4 (s, 9H), 1.6-1.8 (t, 6H), 3.7 (s, 3H), 4.0-
4.1 (dd, RH), 4.5-4.7 (m, RH), 4.8-4.9 (br, 1H), 6.4 (d, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (631 mg, 98% yield).
Pentapeptide 1c-2a-3a-4a-5a. Pentapeptide 1c-2a-3a-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 204 mg (0.48 mmol, 1.1 equiv) of amine 1c-2a-3a, 114
mg (0.44 mmol, 1.0 equiv) of acid, 0.39 mL (5 equiv) of DIPEA,
106 mg (0.33 mmol, 0.75 equiv) of TBTU, and 125 mg (0.33 mmol,
0.75 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(120 mg, 37% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (400 MHz,
CD3OD) δ 0.7-0.9 (m, 24H), 1.4 (s, 9H), 1.5-1.7 (m, 6H), 3.0-
3.1 (m, 2H), 3.5 (s, 3H), 4.1 (d, RH), 4.2 (d, RH), 4.4 (t, RH),
4.5-4.6 (m, 2RH), 4.6-4.7 (m, 2H), 5.0 (d, 1H), 7.1-7.3 (m, 4H),
7.4-7.5 (m, 1H), 7.5-7.6 (m, 1H), 7.6 (d, 1H).
Macrocycle 1c-2a-3a-4a-5a (Compound 1). Macrocycle 1c-
2a-3a-4a-5a (compound 1) was synthesized following the Macro-
cyclization procedure, utilizing 92.7 mg (0.15 mmol, 1.0 equiv) of
linear pentapeptide, 0.13 mL (5 equiv) of DIPEA, 48.5 mg (0.15
mmol, 1.0 equiv) of TBTU, 57.4 mg (0.15 mmol, 1.0 equiv) HATU,
and 45.1 mg (0.15 mmol, 1.0 equiv) of DEPBT. The crude reaction
was purified by reverse phase HPLC to yield the macrocycle (38
1
mg, 42% yield): Rf 0.5 (EtOAc/Hex 4:3); H NMR (400 MHz,
CD3OD) δ 0.8-1.0 (m, 24H), 1.6-1.8 (m, 9H), 3.1-3.2 (m, 2H),
4.2 (m, RH), 4.3 (m, RH), 4.5 (t, RH), 4.7 (m, RH), 5.0 (m, RH),
5.2 (d, 1H), 7.2-7.3 (m, 4H), 7.3 (d, 1H), 7.5 (m, 1H), 7.7 (s,
1H); LCMS m/z calcd for C33H51N5O5 (M + 1) 598.39, found 598.3.
Synthesis of Compound 2. Dipeptide 1f-2a. Dipeptide 1f-2a
was synthesized following the General Peptide Synthesis procedure,
utilizing 614 mg (2.6 mmol, 1.1 equiv) of amine 1a, 600 mg (2.4
mmol, 1.0 equiv) of acid, 1.7 mL (4 equiv) of DIPEA, and 865 mg
(2.9 mmol, 1.1 equiv) of DEPBT. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
dipeptide (880 mg, 89% yield): Rf 0.65 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.9-1.0 (d, 6H), 1.4 (s, 9H), 1.6 (br, 1H),
2.0 (s, 2H), 3.0 (m, 2H), 3.7 (s, 3H), 4.1 (dd, RH), 4.8 (dd, RH),
6.7 (s, 1H), 6.8 (s, 1H), 6.8 (d, 2H), 7.0 (d, 2H), 7.2 (s, 1H).
Dipeptide 1f-2a-NH2. Dipeptide 1f-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (664 mg, 100% yield).
Synthesis of Compound 1. Dipeptide 1c-2a. Dipeptide 1c-2a
was synthesized following the General Peptide Synthesis procedure,
utilizing 344 mg (1.8 mmol, 1.1 equiv) of amine 1c, 408 mg (1.6
mmol, 1.0 equiv) of acid, 1.1 mL (4 equiv) of DIPEA, 395 mg
(1.2 mmol, 0.75 equiv) of TBTU, and 467 mg (1.2 mmol, 0.75
equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (635
1
mg, 92% yield): Rf 0.5 (EtOAc/Hex 3:4); H NMR (200 MHz,
CDCl3) δ 1.0-1.2 (m, 6H), 1.4 (s, 9H), 1.6 (m, 2H), 1.8-2.0 (m,
1H), 3.2-3.2 (m, 2H), 3.7 (s, 3H), 4.8-5.1 (s, 2H), 5.3 (br, RH),
5.5 (m, RH), 7.2-7.4 (m, 4H), 8.1 (m, 1H).
Dipeptide 1c-2a-NH2. Dipeptide 1c-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (486 mg, 100% yield).
Tripeptide 1c-2a-3a. Tripeptide 1c-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 243
mg (0.75 mmol, 1.1 equiv) of amine 1c-2a, 149 mg (0.68 mmol,
1.0 equiv) of acid, 0.6 mL (5 equiv) of DIPEA, and 275 mg (0.85
mmol, 1.25 equiv) of TBTU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (253 mg, 71% yield): Rf 0.5 (EtOAc/Hex 3:4); 1H NMR
(200 MHz, CDCl3) δ 0.9-1.1 (m, 12H), 1.5 (s, 9H), 1.6-1.8 (m,
Tripeptide 1f-2a-3a. Tripeptide 1f-2a-3a was synthesized fol-
lowing the General Peptide Synthesis procedure, utilizing 664 mg
(2.15 mmol, 1.1 equiv) of amine 1f-2a, 425 mg (1.95 mmol, 1.0
equiv) of acid, 1.36 mL (4 equiv) of DIPEA, and 699 mg (2.3 mmol,
1.1 equiv) of DEPBT. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide (460
1
mg, 50% yield): Rf 0.65 (EtOAc/Hex 3:1); H NMR (200 MHz,
CD3OD) δ 0.8-0.9 (m, 12H), 1.4 (s, 9H), 2.8-3.2 (m, 2H), 3.6
(s, 3H), 3.8 (d, RH), 4.4 (t, RH), 4.6 (dd, RH), 6.6-7.0 (dd, 4H).
Tripeptide 1f-2a-3a-NH2. Tripeptide 1f-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
1990 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
dipeptide was taken on to the next reaction without further
purification or characterization (355 mg, 100% yield).
Tripeptide 1e-2a-3a-NH2. Tripeptide 1e-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (399 mg, 100% yield).
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 400 mg (2.2
mmol, 1.1 equiv) of amine 4a, 500 mg (2.0 mmol, 1.0 equiv) of
acid, 1.4 mL (4 equiv) of DIPEA, and 770.6 mg (2.4 mmol, 1.1
equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (660
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 799 mg (4.4
mmol, 1.1 equiv) of amine 4a, 1 g (4.0 mmol, 1.0 equiv) of acid,
2.8 mL (4 equiv) of DIPEA, and 1.5 g (1.4 mmol, 1.2 equiv) of
TBTU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (660 mg, 98%
1
mg, 97% yield); Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (dd, 12H), 1.4 (s, 9H), 1.5-1.8 (m, 6H), 3.7 (s,
3H), 4.0 (m, RH), 4.6 (m, RH), 4.8 (br, 1H), 6.4 (br, 1H).
1
yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
0.9-1.0 (d, 12H), 1.4 (s, 9H), 1.5-1.8 (br, 6H), 3.7 (s, 3H), 4.1
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (564 mg, 87.8% yield): 1H NMR (200 MHz,
CDCl3) δ 0.7-0.9 (dd, 12H), 1.2-1.6 (m, 2H), 1.4 (s, 9H), 2.0-
2.2 (m, 2H), 3.2-3.3 (m, 2H), 3.6 (s, 3H), 3.8 (dd, RH), 4.2 (m,
RH), 4.8 (quint, RH), 4.9 (br, 1H), 6.3 (br, 1H), 6.6 (br, 1H), 7.0-
7.6 (m, 5H), 8.2 (br, 1H).
(dd, RH), 4.6 (dd, RH), 4.9 (d, 1H), 6.4 (d, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (564 mg, 89% yield).
Pentapeptide 1e-2a-3a-4a-5a. Pentapeptide 1e-2a-3a-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 399 mg (0.92 mmol, 1.1 equiv) of amine 1e-2a-3a, 371
mg (0.84 mmol, 1.0 equiv) of acid, 600 µL (4 equiv) of DIPEA,
and 301 mg (1.01 mmol, 1.2 equiv) of DEPBT. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the pentapeptide (194 mg, 30% yield): Rf 0.5 (EtOAc/
Pentapeptide 1f-2a-3a-4a-5a. Pentapeptide 1f-2a-3a-4a-5a was
synthesized following the General peptide Synthesis procedure,
utilizing 355 mg (0.00087 mmol, 1.1 equiv) of amine 1f, 416 mg
(0.00079 mmol, 1.0 equiv) of acid, 0.55 mL (4 equiv) of DIPEA,
and 283.4 mg (0.95 mmol, 1.2 equiv) of Depbt. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the pentapeptide (252 mg, 43.4% yield): Rf 0.6 (EtOAc/
1
Hex 3:1); H NMR (500 MHz, CD3OD) δ 0.8-1.0 (m, 24H), 1.4
(m, 9H), 1.5-1.7 (m, 2H), 1.9-2.1 (d, 4H), 3.1 (m, 2H), 3.7 (s,
3H), 4.1 (d, 2RH), 4.3-4.4 (m, 2RH), 4.7 (m, RH), 7.0-7.1 (m,
4H), 7.2 (m, 1H), 7.3 (d, 1H), 7.5 (d, 1H), 7.8 (d, 1H), 8.0 (d, 1H).
1
Hex 3:1); H NMR (500 MHz, CD3OD) δ 0.8 (dd, 6H), 0.9-2.0
(m, 18H), 1.2-1.6 (m, 6H), 1.4 (s, 9H), 1.7 (m, 3H), 2.1 (m, 2H),
2.8-3.1 (m, 2H), 3.7 (s, 3H), 4.1 (m, 2RH), 4.4 (m, 2RH), 4.6 (m,
RH), 6.7-7.0 (dd, 4H).
Macrocycle 1e-2a-3a-4a-5a (Compound 3). Macrocycle 1e-
2a-3a-4a-5a (compound 3) was synthesized following the Macro-
cyclization procedure, utilizing 167 mg (0.26 mmol, 1.0 equiv) of
linear pentapeptide, 360 µL (8 equiv) of DIPEA, 42 mg (0.13 mmol,
0.5 equiv) of TBTU, 49.4 mg (0.13 mmol, 0.5 equiv) HATU, and
39 mg (0.13 mmol, 0.5 equiv) of DEPBT. The crude reaction was
purified by reverse phase HPLC to yield the macrocycle (5.5 mg,
Macrocycle 1f-2a-3a-4a-5a (Compound 2). Macrocycle 1f-2a-
3a-4a-5a (compound 2) was synthesized following the Macrocy-
clization procedure, utilizing 210.8 mg (0.34 mmol, 1.0 equiv) of
linear pentapeptide, 0.48 mL (4 equiv) of DIPEA, 55.4 mg (0.17
mmol, 0.5 equiv) of TBTU, 68.2 mg (0.179 mmol, 0.5 equiv)
HATU, and 51.4 mg (0.171 mmol, 0.5 equiv) of DEPBT. The crude
reaction was purified by reverse phase-HPLC to yield the macro-
cycle (8.0 mg, 5% yield): Rf 0.6 (EtOAc/Hex 1:0); 1H NMR (500
MHz, CD3OD) δ 0.6-0.8 (dd, 6H), 0.9-1.0 (m, 18H), 1.2-1.7
(m, 10H), 2.6-2.9 (m, 2H), 3.2 (m, RH), 4.1 (m, RH), 4.3 (m,
RH), 4.4 (m, RH), 4.5 (m, RH), 6.7-7.0 (dd, 4H), 7.2 (d, 1H), 8.1
(d, 1H), 8.2 (d, 1H), 8.4 (d, 1H), 8.7 (d, 1H); LCMS m/z calcd for
C32H51N5O6 (M + 1) 601.77, found 602.4.
Synthesis of Compound 3. Dipeptide 1e-2a. Dipeptide 1e-2a
was synthesized following the General Peptide Synthesis procedure,
utilizing 560.56 mg (2.2 mmol, 1.1 equiv) of amine 1e, 500 mg
(2.0 mmol, 1.0 equiv) of acid, 1.4 mL (4 equiv) of DIPEA, and
717.6 mg (2.39 mmol, 1.2 equiv) of DEPBT. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the dipeptide (650 mg, 82% yield): Rf 0.65 (EtOAc/Hex
1:1); 1H NMR (200 MHz, CDCl3) δ 0.8 (d, 6H), 1.4 (s, 9H), 1.5-
1.7 (m, 3H), 3.3 (d, 2H), 3.6 (s, 3H), 4.0 (m, RH), 4.9 (m, RH), 4.8
(br, 1H), 6.6 (br, 1H), 7.0-7.5 (m, 5H), 8.1 (br, 1H).
1
33% yield): Rf 0.65 (EtOAc/MeOH 98:2); H NMR (500 MHz,
CD3OD) δ 0.8-1.0 (m, 24H), 1.2-1.4 (m, 6H), 1.5-1.7 (m, 4H),
3.1-3.2 (m, 2H), 3.6-3.8 (m, 2RH), 4.0 (d, RH), 4.5 (m, RH), 4.6
(m, RH), 6.6 (d, 1H), 7.1-7.2 (m, 4H), 7.3 (d, 4H), 7.4 (m, 1H),
7.5 (d, 1H), 8.0 (d, 1H), 8.1 (d, 1H); LCMS m/z calcd for
C34H52N6O5 (M + 1) 625.4, found 625.5.
Synthesis of Compound 4. Dipeptide 1b-2a. Dipeptide 1b-2a
was synthesized following the General Peptide Synthesis procedure,
utilizing 475 mg (2.2 mmol, 1.1 equiv) of amine 1b, 500 mg (2.0
mmol, 1.0 equiv) of acid, 1.39 mL (4 equiv) of DIPEA, and 708
mg (2.2 mmol, 1.1 equiv) of TBTU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
1
dipeptide (721 mg, 92% yield): Rf 0.5 (EtOAc/Hex 35:65); H
NMR (200 MHz, CDCl3) δ 1.0 (d, 6H), 1.5 (s, 9H), 1.7 (m, 3H),
3.1-3.3 (sept, 2H), 3.8 (s, 3H), 4.2 (m, RH), 4.8 (br, 1H), 5.0 (q,
RH), 6.6 (br, 1H), 7.2-7.4 (m, 5H).
Dipeptide 1b-2a-NH2. Dipeptide 1b-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (537 mg, assume quantitative yield).
Tripeptide 1b-2a-3a. Tripeptide 1b-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 537
mg (1.83 mmol, 1.1 equiv) of amine 1b-2a, 363 mg (1.67 mmol,
1.0 equiv) of acid 3a, 1.17 mL (4 equiv) of DIPEA, and 590.4 mg
(1.83 mmol, 1.1 equiv) of TBTU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (798 mg, 97% yield): Rf 0.6 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.57 (s, 9H), 1.6-1.7 (m,
3H), 2.1-2.3 (sept, 1H), 3.1-3.4 (m, 2H), 3.8 (s, 3H), 3.9-4.0
(dd, RH), 4.5 (m, RH), 4.8-5.0 (q, RH), 5.0 (br, 1H), 6.4 (d, 1H),
6.6 (br, 1H), 7.2-7.4 (m, 5H).
Dipeptide 1e-2a-NH2. Dipeptide 1e-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (498 mg, 100% yield).
Tripeptide 1e-2a-3a. Tripeptide 1e-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 498
mg (1.5 mmol, 1.1 equiv) of amine 1e-2a, 295.5 mg (1.36 mmol,
1.0 equiv) of acid, 0.95 mL (4 equiv) of DIPEA, and 488 mg (1.63
mmol, 1.2 equiv) of DEPBT. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (488 mg, 67% yield): Rf 0.55 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.7-0.9 (dd, 12H), 1.2-1.6 (m, 2H), 1.4 (s,
9H), 2.0-2.2 (m, 2H), 3.2-3.3 (m, 2H), 3.6 (s, 3H), 3.8 (dd, RH),
4.2 (m, RH), 4.8 (quint, RH), 4.9 (br, 1H), 6.3 (br, 1H), 6.6 (br,
1H), 7.0-7.6 (m, 5H), 8.2 (br, 1H).
Tripeptide 1b-2a-3a-NH2. Tripeptide 1b-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
J. Org. Chem, Vol. 72, No. 6, 2007 1991

Rodriguez et al.
dipeptide was taken on to the next reaction without further
purification or characterization (635 mg, assume quantitative yield).
Dipeptide 4c-5b. Dipeptide 4c-5b was synthesized following
the General Peptide Synthesis procedure, utilizing 780 mg (3.99
mmol, 1.1 equiv) of amine 4c, 904 mg (3.63 mmol, 1.0 equiv) of
acid 5b, 2.53 mL (4 equiv) of DIPEA, 875 mg (2.2 mmol, 0.75
equiv) of TBTU, and 690 mg (1.8 mmol, 0.5 equiv) of HATU.
The crude reaction was purified by column chromatography (silica
gel, EtOAc/Hex) to yield the dipeptide (140 mg, 15% yield): Rf
0.6 (EtOAc/Hex 35:65); H NMR (200 MHz, CDCl3) δ 1.0-1.2
(m, 12H), 1.4-1.7 (m, 4H), 1.5 (s, 9H), 1.7-2.0 (m, 2H), 3.1 (s,
3H), 3.8 (s, 3H), 4.8 (br, RH), 5.3 (m, RH).
Dipeptide HO-4c-5b. Dipeptide HO-4c-5b was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (133 mg, 99% yield).
1.2 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (720
mg, 99% yield): Rf 0.5 (EtOAc/Hex 7:13); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-1.8 (m, 6H), 3.7 (s,
3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H), 6.5 (br, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (693 mg, 97% yield).
1
1
Pentapeptide 1a-2g-3a-4a-5a. Pentapeptide 1a-2g-3a-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 960 mg (2.173 mmol, 1.1 equiv) of amine 1a-2g-3a-NH2,
680 mg (1.975 mmol, 1.0 equiv) of acid HO-4a-5a, 2800 µL (8
equiv) of DIPEA, 440 mg (1.381 mmol, 0.7 equiv) of TBTU, and
520 mg (1.381 mmol, 0.7 equiv) of HATU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the pentapeptide (900 mg, 60% yield): Rf 0.5 (EtOAc/
Pentapeptide 1b-2a-3a-4c-5b. Pentapeptide 1b-2a-3a-4c-5b was
synthesized following the General Peptide Synthesis procedure,
utilizing 192 mg (0.49 mmol, 1.1 equiv) of amine 1b-2a-3a, 160
mg (0.44 mmol, 1.0 equiv) of acid 4c-5b, 0.32 mL (4 equiv) of
DIPEA, 78 mg (0.24 mmol, 0.55 equiv) of TBTU, and 93 mg (0.24
mmol, 0.55 equiv) HATU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
1
Hex 3:2); H NMR (500 MHz, CDCl3) δ 0.4-0.7 (dd, 6H), 0.9
(m, 12H), 1.2 (t, 3H), 1.4 (s, 9H), 1.6 (m, 4H), 2.9 (s, 3H), 3.0-
3.2 (m, 4H), 3.7 (s, 3H), 4.0 (m, RH), 4.4-4.8 (m, 2RH), 4.9 (br,
1H), 5.6 (dd, RH), 6.4-6.6 (d, 2H), 7.0-7.4 (m, 10H).
Macrocycle 1a-2g-3a-4a-5a (Compound 6). Macrocycle 1a-
2g-3a-4a-5a (compound 6) was synthesized following the Macro-
cyclization procedure, utilizing 169 mg (0.2590 mmol, 1.0 equiv)
of linear pentapeptide, 450 µL (10 equiv) of DIPEA, 49 mg (0.1291
mmol, 0.5 equiv) of TBTU, 42 mg (0.1291 mmol, 0.5 equiv) of
HATU, and 39 mg (0.1291 mmol, 0.5 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (25 mg, 16% yield): Rf 0.5 (EtOAc/Hex 13:7); 1H NMR (500
MHz, CDCl3) δ 0.6-1.1 (m, 18H), 1.3-1.8 (m, 3H), 2.8-3.0 (m,
2H), 2.9 (s, 3H), 3.0-3.3 (m, 2H), 4.1 (br, RH), 4.5 (q, RH), 4.6
(br, RH), 5.2 (m, RH), 6.5-6.9 (br, 2H), 7.1-7.3 (m, 10H), 7.5
(br, 1H); LCMS m/z calcd for C36H51N5O5 (M + 1) 634.39, found
634.3.
1
pentapeptide (315 mg, 97% yield): Rf 0.5 (EtOAc/Hex 1:1); H
NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.4 (s, 9H), 1.4-
2.1 (m, 10H), 3.0 (s, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-4.2
(m, RH), 4.4 (m, RH), 4.6 (m, RH), 4.8 (m, RH), 5.1 (m, RH),
7.1-7.3 (m, 5H).
Macrocycle 1b-2a-3a-4c-5b (Compound 4). Macrocycle 1b-
2a-3a-4c-5b (compound 4) was synthesized following the Macro-
cyclization procedure, utilizing 200 mg (0.33 mmol, 1.0 equiv) of
linear pentapeptide precursor, 0.35 mL (6 equiv) of DIPEA, 53
mg (0.16 mmol, 0.5 equiv) of TBTU, 63 mg (0.16 mmol, 0.5 equiv)
of HATU, and 50 mg (0.16 mmol, 0.5 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (7 mg, 3.6% yield): Rf 0.4 (EtOAc ) 100%); LCMS m/z
calcd for C33H53N5O5 (M + 1) 600.8, found 600.8.
Synthesis of Compound 7. Dipeptide 1a-2f. Dipeptide 1a-2f
was synthesized following the General Peptide Synthesis procedure,
utilizing 630 mg (2.9 mmol, 1.1 equiv) of amine 1a, 700 mg (2.6
mmol, 1.0 equiv) of acid, 1.8 mL (4 equiv) of DIPEA, and 1.0 g
(3.2 mmol, 1.2 equiv) of TBTU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
Synthesis of Compound 6. Dipeptide 1a-2g. Dipeptide 1a-2g
was synthesized following the General Peptide Synthesis procedure,
utilizing 690 mg (3.199 mmol, 1.2 equiv) of amine 1a, 812 mg
(2.908 mmol, 1.0 equiv) of acid 2g, 2000 µL (4 equiv) of DIPEA,
and 1120 mg (3.489 mmol, 1.2 equiv) of TBTU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the dipeptide (1282 mg, 90% yield): Rf 0.5 (EtOAc/Hex
1
dipeptide (1.1g, 98% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR
(200 MHz, CDCl3) δ 1.4 (s, 9H), 2.0-3.1 (m, 4H), 3.6 (s, 3H),
4.3 (dd, RH), 4.7-4.9 (br, 1H), 4.8-4.9 (dd, RH), 6.3 (d, 1H) 6.9-
7.3 (m, 10H).
Dipeptide 1a-2f-NH2. Dipeptide 1a-2f-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (840 mg, 100% yield).
1
1:1); H NMR (200 MHz, CDCl3) δ 1.6 (s, 9H), 2.7 (s, 3H), 3.1
(br, 4H), 3.7 (s, 3H), 4.7-5.0 (br, 2RH), 6.6 (br, 1H) 7.0-7.4 (m,
10H).
Dipeptide 1a-2g-NH2. Dipeptide 1a-2g-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (991 mg, quantitative yield).
Tripeptide 1a-2f-3a. Tripeptide 1a-2f-3a was synthesized fol-
lowing the General Peptide Synthesis procedure, utilizing 840 mg
(2.6 mmol, 1.1 equiv) of amine 1a-2f, 510 mg (2.3 mmol, 1.0 equiv)
of acid, 1.6 mL (4 equiv) of DIPEA, and 900 mg (2.8 mmol, 1.2
equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide
Tripeptide 1a-2g-3a. Tripeptide 1a-2g-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 870
mg (2.557 mmol, 1.1 equiv) of amine 1a-2g-NH2, 505 mg (2.324
mmol, 1.0 equiv) of acid 3a, 1600 µL (4 equiv) of DIPEA, and
895 mg (2.789 mmol, 1.2 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the tripeptide (1250 mg, 72% yield): Rf 0.5 (EtOAc/Hex 13:7); 1H
NMR (200 MHz, CDCl3) δ 0.5-0.7 (m, 6H), 1.4 (s, 9H), 1.6 (m,
1H), 2.9 (s, 3H), 3.1 (t, 4H), 3.6 (s, 3H), 4.2 (dd, RH), 4.8 (q, RH),
5.0 (br, 1H), 5.5 (dd, RH), 6.7 (br, 1H), 7.1-7.4 (m, 10H).
Tripeptide 1a-2g-3a-NH2. Tripeptide 1a-2g-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (1018 mg, quantitative yield).
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 400 mg (2.206
mmol, 1.1 equiv) of amine 4a, 500 mg (2.006 mmol, 1.0 equiv) of
acid 5a, 1400 µL (4 equiv) of DIPEA, and 770 mg (2.399 mmol,
1
(1.2g, 91% yield): Rf 0.5 (EtOAc/Hex 5:3); H NMR (200 MHz,
CDCl3) δ 0.7-0.9 (dd, 6H), 1.4 (s, 9H), 2.0 (m, 1H), 2.9-3.1 (m,
4H), 3.6 (s, 3H), 3.9 (t, RH), 4.7-4.9 (m, 2H), 5.1 (d, RH), 6.5-
6.6 (d, RH), 6.5-6.7 (br, 1H), 7.0-7.3 (m, 10H).
Tripeptide 1a-2f-3a-NH2. Tripeptide 1a-2f-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (910 mg, 100% yield).
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 800 mg (4.4
mmol, 1.1 equiv) of amine 4a, 1.0 g (4.0 mmol, 1.0 equiv) of acid,
2.8 mL (4 equiv) of DIPEA, and 1.5 g (4.8 mmol, 1.2 equiv) of
TBTU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (1.4 g, 100% yield):
1
Rf 0.5 (EtOAc/Hex 3:5); H NMR (200 MHz, CDCl3) δ 0.9-1.0
1992 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
(d, 12H), 1.4 (s, 9H), 1.5-1.8 (br, 6H), 3.7 (s, 3H), 4.1 (dd, RH),
4.6 (dd, RH), 4.9 (d, 1H), 6.4 (d, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1.3 g, 100% yield).
was taken on to the next reaction without further purification or
characterization (1340 mg, 93% yield).
Pentapeptide 1a-2e-3a-4f-5d. Pentapeptide 1a-2e-3a-4f-5d was
synthesized following the General Peptide Synthesis procedure,
utilizing 400 mg (0.87 mmol, 1.1 equiv) of amine 1a-2e-3a, 250
mg (0.79 mmol, 1.0 equiv) of acid 4f-5d, 0.69 mL (5 equiv) of
DIPEA, 152 mg (0.47 mmol, 0.6 equiv) of TBTU, and 300 mg
(0.79 mmol, 1.0 equiv) of HATU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
Pentapeptide 1a-2f-3a-4a-5a. Pentapeptide 1a-2f-3a-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 920 mg (2.2 mmol, 1.1 equiv) of amine 1a-2f-3a, 680 mg
(2.0 mmol, 1.0 equiv) of acid, 2.8 mL (8 equiv) of DIPEA, 440
mg (1.4 mmol, 0.7 equiv) of TBTU, and 520 mg (1.4 mmol, 0.7
equiv) HATU. The crude reaction was purified by column chro-
matography (silica gel, EtOAc/Hex) to yield the pentapeptide (200
1
pentapeptide (310 mg, 52% yield): Rf 0.4 (EtOAc/Hex 1:1); H
NMR (500 MHz, DMSO-d6) δ 0.8 (dd, 18H), 1.4 (9H), 1.8-2.0
(m, 2H), 2.8-3.0 (m, 2H), 3.4 (d, 2H), 3.6 (s, 3H), 3.8 (t, RH), 4.2
(dd, RH), 4.3 (m, RH), 4.4 (s, 2H), 4.5 (m, RH), 4.6 (m, RH), 6.8
(d, 1H), 7.1-7.3 (m, 10H), 7.6 (d, 1H), 7.8 (d, 1H), 8.0 (d, 1H),
8.4 (d, 1H).
Macrocycle 1a-2e-3a-4f-5d (Compound 9). Macrocycle 1a-2e-
3a-4f-5d was synthesized following the Macrocyclization procedure,
utilizing 150 mg (0.23 mmol, 1.0 equiv) of linear pentapeptide,
0.2 mL (5 equiv) of DIPEA, 73 mg (0.23 mmol, 1.0 equiv) of
TBTU, and 87 mg (0.23 mmol, 1.0 equiv) of HATU. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (20 mg, 14% yield): Rf 0.5 (EtOAc/Hex 3:1); LCMS m/z
calcd for C34H47N5O6 (M + 1) 622.77, found 621.9.
1
mg, 13% yield): Rf 0.5 (EtOAc/Hex 5:3); H NMR (200 MHz,
DMSO) δ 0.4-0.6 (dd, 6H), 0.8-1.0 (d, 12H), 1.4 (s, 9H), 1.5-
1.8 (br, 4H), 2.9 (d, 1H), 3.6 (s, 3H), 3.9 (dd, RH), 4.1 (d, RH), 4.4
(d, RH), 4.5 (d, RH), 6.9 (d, 1H), 7.0-7.4 (m, 10H), 7.6 (d, 1H),
7.8 (d, 1H), 8.2 (d, 1H), 8.5 (d, 1H).
Macrocycle 1a-2f-3a-4a-5a (Compound 7). Macrocycle 1a-2f-
3a-4a-5a (compound 7) was synthesized following the Macrocy-
clization procedure, utilizing 100 mg (0.16 mmol, 1.0 equiv) of
linear pentapeptide, 0.28 mL (10 equiv) of DIPEA, 25 mg (0.08
mmol, 0.5 equiv) of TBTU, 35 mg (0.08 mmol, 0.5 equiv) HATU,
and 23 mg (0.08 mmol, 0.5 equiv) of DEPBT. The crude reaction
was purified by reverse phase HPLC to yield the macrocycle (10
mg, 10% yield): Rf 0.5 (EtOAc/Hex 5:3); LCMS m/z calcd for
C35H49N5O5 (M + 1) 620.37, found 620.3.
Synthesis of Compound 10. Dipeptide 1a-2e. Dipeptide 1a-2e
was synthesized following the General Peptide Synthesis procedure,
utilizing 435 mg (1.19 mmol, 1.1 equiv) of amine 1a, 500 mg (1.65
mmol, 1.0 equiv) of acid 2e, 865 µL (4 equiv) of DIPEA, and 790
mg (2.48 mmol, 1.5 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
Synthesis of Compound 9. Dipeptide 1a-2e. Dipeptide 1a-2e
was synthesized following the General Peptide Synthesis procedure,
utilizing 430 mg (2.03 mmol, 1.2 equiv) of amine 1a, 500 mg (1.65
mmol, 1.0 equiv) of acid 2e, 0.86 mL (3 equiv) of DIPEA, and
790 mg (2.47 mmol, 1.5 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
1
the dipeptide (750 mg, 100% yield): Rf 0.7 (EtOAc/Hex 1:1); H
NMR (200 MHz, CDCl3) δ 1.4 (s, 9H), 3.0-3.1 (m, 2H), 3.4-3.5
(q, 1H), 3.6 (s, 3H), 3.8 (m, 1H), 4.3 (br, RH), 4.4-4.5 (q, 2H),
4.8 (br, RH), 5.3 (br, 1H), 6.4-6.5 (br, 1H) 7.1-7.4 (m, 10H).
Dipeptide 1a-2e-NH2. Dipeptide 1a-2e-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (586 mg, 100% yield).
1
the dipeptide (740 mg, 98% yield): Rf 0.6 (EtOAc/Hex 1:1); H
NMR (200 MHz, CDCl3) δ 1.4 (s, 9H), 3.0-3.2 (sept, 2H), 3.4-
3.8 (m, 2H), 3.6 (s, 3H), 4.2 (br, RH), 4.4 (dd, 2H), 4.8 (q, RH),
5.3 (br, 1H), 6.9 (br, 1H), 7.0-7.4 (m, 10H).
Dipeptide 1a-2e-NH2. Dipeptide 1a-2e-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (578 mg, assume quantitative yield).
Tripeptide 1a-2e-3a. Tripeptide 1a-2e-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 1000
mg (2.8 mmol, 1.3 equiv) of amine 1a-2e, 460 mg (2.1 mmol, 1.0
equiv) of acid, 1.47 mL (4 equiv) of DIPEA, 670 mg (2.1 mmol,
1.0 equiv) of TBTU, and 399 mg (1.05 mmol, 0.5 equiv) of HATU.
The crude reaction was purified by column chromatography (silica
gel, EtOAc/Hex) to yield the tripeptide (870 mg, 75% yield): Rf
0.5 (EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.8-1.0 (dd,
6H), 1.4 (s, 9H), 2.0-2.2 (sept, 1H), 3.0-3.2 (m, 2H), 3.4-4.0
(m, 2H), 3.6 (s, 3H), 3.8-4.0 (m, RH), 4.5 (dd, 2H), 4.6 (m, RH),
4.8 (q, RH), 5.0 (br, 1H), 6.7 (br, 1H), 6.9 (br, 1H), 7.0-7.4 (m,
10H).
Tripeptide 1a-2e-3a. Tripeptide 1a-2e-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 500
mg (1.40 mmol, 1.3 equiv) of amine 1a-2e-NH2, 230 mg (1.05
mmol, 1.0 equiv) of acid 3a, 735 µL (4 equiv) of DIPEA, 335 mg
(1.05 mmol, 1.0 equiv) of TBTU, and 200 mg (0.525 mmol, 0.5
equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide
1
(467.3 mg, 80% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200
MHz, CDCl3) δ 0.8-1.0 (m, 6H), 1.4 (s, 9H), 2.0-2.2 (m, 1H),
3.0-3.2 (d, 2H), 3.5 (m, 1H), 3.7 (s, 3H), 3.9 (m, 2H), 4.4-4.5
(m, 2H), 4.6 (m, RH), 4.8 (m, RH), 5.0 (br, 1H), 6.7 (br, 1H), 6.9
(br, 1H), 7.0-7.3 (m, 10H).
Tripeptide 1a-2e-3a-NH2. Tripeptide 1a-2e-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (383.3 mg, 100% yield).
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 400.5 mg (2.21
mmol, 1.1 equiv) of amine 4a, 500 mg (2.01 mmol, 1.0 equiv) of
acid 5a, 1400 µL (4 equiv) of DIPEA, and 708.3 mg (2.21 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (721
Tripeptide 1a-2e-3a-NH2. Tripeptide 1a-2e-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (713 mg, assume quantitative yield).
Dipeptide 4f-5d. Dipeptide 4f-5d was synthesized following the
General Peptide Synthesis procedure, utilizing 920 mg (5.5 mmol,
1.2 equiv) of amine 4f, 1000 mg (4.6 mmol, 1.0 equiv) of acid 5d,
2.4 mL (3 equiv) of DIPEA, and 2210 mg (6.9 mmol, 1.5 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (1440 mg, 94%
1
mg, 100% yield): Rf 0.7 (EtOAc/Hex 1:1); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-1.8 (m, 6H), 3.7 (s,
3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H), 6.4 (br, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (693.3 mg, 97% yield).
Pentapeptide 1a-2e-3a-4a-5a. Pentapeptide 1a-2e-3a-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 383.2 mg (1.05 mmol, 1.1 equiv) of amine 1a-2e-3a-NH2,
1
yield): Rf 0.5 (EtOAc/Hex 35:65); H NMR (200 MHz, CDCl3)
0.9-1.0 (dd, 12H), 1.4 (s, 9H), 2.0-2.2 (sept, 2H), 3.7 (s, 3H),
3.8-4.0 (dd, RH), 4.5 (dd, RH), 5.0 (br, 1H), 6.4 (br, 1H).
Dipeptide HO-4d-5d. Dipeptide HO-4f-5d was synthesized
following the General Acid Deprotection procedure. This dipeptide
J. Org. Chem, Vol. 72, No. 6, 2007 1993

Rodriguez et al.
1
330 mg (1.05 mmol, 1.0 equiv) of acid HO-4a-5a, 492 µL (4 equiv)
of DIPEA, 153 mg (0.475 mmol, 0.5 equiv) of TBTU, and 216.7
mg (0.570 mmol, 0.6 equiv) of HATU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the pentapeptide (446.7 mg, 60% yield): Rf 0.7 (EtOAc/Hex 3:1);
1H NMR (500 MHz, CDCl3) δ 0.8-1.0 (br, 18H), 1.4 (s, 9H), 1.5-
1.8 (m, 6H), 2.0-2.2 (m, 1H), 3.0-3.2 (m, 2H), 3.4-3.5 (m, 1H),
3.6 (s, 3H), 3.8 (m, 1H), 4.1-4.3 (br, 2RH), 4.4-4.5 (br, 2RH),
4.8 (br, RH), 5.1 (br, 1H), 5.3 (br, 1H), 6.7 (br, 1H), 6.9 (br, 1H),
7.1-7.4 (m, 10H).
mg, 90% yield): Rf 0.7 (EtOAc/Hex 1:1); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.6-1.8 (m, 6H), 3.7 (s,
3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H), 6.4 (br, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (520 mg, 90% yield).
Pentapeptide 1a-2b-3e-4a-5a. Pentapeptide 1a-2b-3e-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 457 mg (1.1 equiv) of amine 1a-2b-3e-NH2, 390 mg (1.13
mmol, 1.0 equiv) of acid HO-4a-5a, 800 µL (4 equiv) of DIPEA,
180 mg (0.56 mmol, 0.5 equiv) of TBTU, and 429.4 mg (1.13
mmol, 1.0 equiv) HATU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
pentapeptide (557 mg, 64% yield): Rf 0.7 (EtOAc/Hex 3:1); H
3OD) δ 0.8-1.0 (m, 21H), 1.4 (s, 9H), 1.5-
1.8 (m, 11H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.1 (m, 2RH), 4.4 (br,
Protected Macrocycle 1a-2e-3a-4a-5a. Macrocycle 1a-2e-3a-
4a-5a was synthesized following the Macrocyclization procedure,
utilizing 200 mg (0.3 mmol, 1.0 equiv) of linear pentapeptide, 200
µL (4 equiv) of DIPEA, 48 mg (0.15 mmol, 0.5 equiv) of TBTU,
57 mg (0.15 mmol, 0.5 equiv) of HATU, and 45 mg (0.15 mmol,
0.5 equiv) of DEPBT. The crude reaction was purified by reverse
phase HPLC to yield the macrocycle (20 mg, 10% yield): Rf 0.5
1
NMR (500 MHz, CD
1
(EtOAc/Hex 3:1); H NMR (500 MHz, CD3OD) δ 0.8-1.0 (m,
2RH), 4.6 (m, RH), 7.1-7.3 (m, 5H).
18H), 1.5-1.7 (m, 6H), 2.0 (m, 1H), 2.9 (m, 2H), 3.5 (m, 1H), 3.9
(m, RH), 4.1 (m, RH), 4.4 (m, RH), 4.5 (m, RH), 4.6 (m, RH),
7.1-7.4 (m, 10H), 7.7 (m, 1H), 7.9 (m, 1H), 8.3 (m, 1H), 8.6 (m,
1H), 8.7 (m, 1H); LCMS m/z calcd for C36H51N5O6 (M + 1) 650.37,
found 650.60.
Macrocycle 1a-2b-3e-4a-5a (Compound 11). Macrocycle 1a-
2b-3e-4a-5a (compound 11) was synthesized following the Mac-
rocyclization procedure, utilizing 233 mg (0.4 mmol, 1.0 equiv) of
linear pentapeptide, 800 µL (4 equiv) of DIPEA, 64 mg (0.2 mmol,
0.5 equiv) of TBTU, 76 mg (0.2 mmol, 0.5 equiv) of HATU, and
60 mg (0.2 mmol, 0.5 equiv) of DEPBT. The crude reaction was
purified by reverse phase HPLC to yield the macrocycle (3 mg,
3% yield): Rf 0.5 (EtOAc/Hex 3:1); 1H NMR (500 MHz, CD3OD)
δ 0.8-1.0 (m, 21H), 1.5-1.8 (m, 11H), 2.8 (m, 2H), 4.0 (m, RH),
4.1 (m, RH), 4.3 (m, RH), 4.5 (m, RH), 4.6 (m, RH), 7.2-7.4 (m,
5H), 7.6 (m, 1H), 7.8 (m, 1H), 8.0 (br, 1H), 8.2 (m, 1H), 8.6 (m,
1H); LCMS m/z calcd for H31H49N5O5 (M + 1) 572.37, found 572.3.
Synthesis of Compound 13. Macrocycle 1a-2e-3a-4f-5d (Com-
pound 13). Deprotected macrocycle 1a-2e-3a-4f-5d (compound 13)
was synthesized utilizing 10 mg (0.016 mmol, 1.0 equiv) of
protected macrocycle, 10% palladium-carbon (cat. amount). The
crude reaction was purified by reverse phase HPLC to yield the
deprotected macrocycle (0.3 mg, 3.7% yield); LCMS m/z calcd for
C27H41N5O6 (M + 1) 532.5, found 533.0.
Synthesis of Compound 16. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 475.8 mg (2.206 mmol, 1.1 equiv) of amine
1a, 500 mg (500 mmol, 1.0 equiv) of acid 2a, 1400 µL (4 equiv)
of DIPEA, and 708.3 mg (2.206 mmol, 1.1 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (716.5 mg, 91% yield): Rf 0.7
(EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H),
1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-
4.2 (m, RH), 4.5-4.7 (br, RH), 4.8-4.9 (br, 1H), 6.4-6.5 (br, 1H)
7.1-7.4 (m, 5H).
Deprotected Macrocycle 1a-2e-3a-4a-5a (Compound 10).
Deprotected macrocycle 1a-2e-3a-4a-5a (compound 10) was
synthesized utilizing 20 mg (0.03 mmol, 1.0 equiv) of protected
macrocycle, 10% palladium-carbon (cat. amount). The crude
reaction was purified by reverse phase HPLC to yield the depro-
1
tected macrocycle (20 mg, 10% yield; 8.0 mg, 95% yield): H NMR
(500 MHz, CD3OD) δ 0.8-1.0 (m, 18H), 1.6-1.8 (m, 6H), 2.0
(m, 1H), 2.9 (m, 2H), 3.6 (m, 1H), 3.9 (m, RH), 4.0 (m, RH), 4.2
(m, RH), 4.5 (m, RH), 5.5 (m, RH), 7.1-7.4 (m, 5H); LCMS m/z
calcd for C29H45N5O5 (M + 1) 560.34, found 560.30.
Synthesis of Compound 11. Dipeptide 1a-2b. Dipeptide 1a-
2b was synthesized following the General Peptide Synthesis
procedure, utilizing 475.8 mg (2.206 mmol, 1.1 equiv) of amine
1a, 500 mg (2.006 mmol, 1.0 equiv) of acid 2b, 1400 µL (4 equiv)
of DIPEA, and 708.3 mg (2.206 mmol, 1.1 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (654 mg, 83% yield): Rf 0.7
(EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H),
1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-
4.2 (m, RH), 4.5-4.7 (br, RH), 4.8-4.9 (br, 1H), 6.4-6.5 (br, 1H)
7.1-7.4 (m, 5H).
Dipeptide 1a-2b-NH2. Dipeptide 1a-2b-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (486 mg, 100% yield).
Tripeptide 1a-2b-3e. Tripeptide 1a-2b-3e was synthesized
following the General Peptide Synthesis procedure, utilizing 486
mg (1.67 mmol, 1.1 equiv) of amine 1a-2b-NH2, 309 mg (1.52
mmol, 1.0 equiv) of acid 3e, 1200 µL (4 equiv) of DIPEA, and
536.3 mg (1.67 mmol, 1.1 equiv) of TBTU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the tripeptide (590 mg, 81% yield): Rf 0.6 (EtOAc/Hex
1:1); 1H NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 9H), 1.4 (s, 9H),
1.5-1.7 (m, 4H), 1.8-2.0 (m, 1H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0 (m, RH), 4.4 (m, RH), 4.8 (m, RH), 4.9 (br, 1H), 6.4 (br, 1H),
6.6 (br, 1H), 7.0-7.3 (m, 5H).
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (534 mg, 100% yield).
Tripeptide 1a-2a-3f. Tripeptide 1a-2a-3f was synthesized fol-
lowing the General Peptide Synthesis procedure, utilizing 500 mg
(1.7 mmol, 1.1 equiv) of amine 1a-2a-NH2, 316 mg (1.55 mmol,
1.0 equiv) of acid 3f, 1100 µL (4 equiv) of DIPEA, 550 mg (1.7
mmol, 1.1 equiv) of TBTU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (548 mg, 83% yield): Rf 0.6 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.8-1.0 (m, 9H), 1.4 (s, 9H), 1.5-1.7 (m,
4H), 1.8-2.0 (m, 1H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0 (m, RH),
4.4 (m, RH), 4.8 (m, RH), 4.9 (br, 1H), 6.4 (br, 1H), 6.6 (br, 1H),
7.0-7.3 (m, 5H).
Tripeptide 1a-2b-3e-NH2. Tripeptide 1a-2b-3e-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (458.3 mg, 100% yield).
Tripeptide 1a-2a-3f-NH2. Tripeptide 1a-2a-3f-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (433.3 mg, 100% yield).
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 401 mg (2.206
Dipeptide 4a-5a. Dipeptide 4a-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 401 mg (2.206
mmol, 1.1 equiv) of amine 4a, 500 mg (2.006 mmol, 1.0 equiv) of
acid 5a, 1400 µL (4 equiv) of DIPEA, and 708.3 mg (2.206 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (620
1994 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
1
mmol, 1.1 equiv) of amine 4a, 500 mg (2.01 mmol, 1.0 equiv) of
acid 5a, 1400 µL (4 equiv) of DIPEA, and 708.3 mg (2.21 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide
yield): Rf 0.7 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
1.0-1.2 (dd, 12H), 1.6 (s, 9H), 2.2-2.4 (sept, 2H), 3.8 (s, 3H),
4.0 (dd, RH), 4.6 (dd, RH), 5.2 (br, 1H), 6.5 (br, 1H).
Dipeptide HO-4f-5d. Dipeptide HO-4f-5d was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1300 mg, 97% yield).
Pentapeptide 1a-2c-3b-4f-5d. Pentapeptide 1a-2c-3b-4f-5d was
synthesized following the General Peptide Synthesis procedure,
utilizing 455 mg (1.15 mmol, 1.1 equiv) of amine 1a-2c-3b, 330
mg (1.05 mmol, 1.0 equiv) of acid 4f-5d, 0.75 mL (4 equiv) of
DIPEA, 170 mg (0.52 mmol, 0.55 equiv) of TBTU, and 200 mg
(0.52 mmol, 0.55 equiv) of HATU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
1
(649.2 mg, 90% yield): Rf 0.7 (EtOAc/Hex 1:1); H NMR (200
MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.6-1.8 (m, 6H),
3.7 (s, 3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H), 6.4 (br, 1H).
Dipeptide HO-4a-5a. Dipeptide HO-4a-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (600 mg, 90% yield).
Pentapeptide 1a-2a-3f-4a-5a. Pentapeptide 1a-2a-3f-4a-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 376.7 mg (1.22 mmol, 1.1 equiv) of amine 1a-2a-3f-NH2,
345.6 mg (1.11 mmol, 1.0 equiv) of acid HO-4a-5a, 850 µL (4
equiv) of DIPEA, 177 mg (0.56 mmol, 0.5 equiv) of TBTU, and
421.8 mg (1.11 mmol, 1.0 equiv) of HATU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the pentapeptide (466 mg, 60% yield): Rf 0.7 (EtOAc/
1
pentapeptide (580 mg, 82% yield): Rf 0.8 (EtOAc/Hex 1:1); H
NMR (300 MHz, DMSO-d6) δ 0.75-0.9 (m, 24H), 1.35 (s, 9H),
1.95 (br, 4H), 3.0 (sept, 2H), 3.55 (s, 3H), 3.7-3.8 (q, RH), 4.2 (t,
2RH), 4.3 (m, RH), 4.4 (q, RH), 7.1-7.3 (m, 5H).
Macrocycle 1a-2c-3b-4f-5d (Compound 17). Macrocycle 1a-
2c-3b-4f-5d (compound 17) was synthesized following the Mac-
rocyclization procedure, utilizing 79 mg (0.14 mmol, 1.0 equiv) of
linear pentapeptide precursor, 0.15 mL (6 equiv) of DIPEA, 27
mg (0.08 mmol, 0.6 equiv) of TBTU, 32 mg (0.08 mmol, 0.6 equiv)
of HATU, and 25 mg (0.08 mmol, 0.6 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
1
Hex 3:1); H NMR (500 MHz, CD3OD) δ 0.8-1.0 (m, 21H), 1.4
(s, 9H), 1.5-1.8 (m, 11H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.1 (m,
2RH), 4.4 (br, 2RH), 4.6 (m, RH), 7.1-7.3 (m, 5H).
Macrocycle 1a-2a-3f-4a-5a (Compound 16). Macrocycle 1a-
2a-3f-4a-5a (compound 16) was synthesized following the Mac-
rocyclization procedure, utilizing 191 mg (0.324 mmol, 1.0 equiv)
of linear pentapeptide, 223 µL (4 equiv) of DIPEA, 42 mg (0.13
mmol, 0.4 equiv) of TBTU, 50 mg (0.13 mmol, 0.4 equiv) of
HATU, and 40 mg (0.13 mmol, 0.4 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (10 mg, 5.4% yield): Rf 0.5 (EtOAc/Hex 3:1); 1H NMR (500
MHz, CD3OD) δ 0.8-1.0 (m, 21H), 1.5-1.8 (m, 11H), 2.8 (m,
2H), 4.0 (m, RH), 4.1 (m, RH), 4.3 (m, RH), 4.5 (m, RH), 4.6 (m,
RH), 7.2-7.4 (m, 5H), 7.6 (m, 1H), 7.8 (m, 1H), 8.0 (br, 1H), 8.2
(m, 1H), 8.6 (m, 1H); LCMS m/z calcd for H31H49N5O5 (M + 1)
) 572.37, found 572.3.
Synthesis of Compound 17. Dipeptide 1a-2c. Dipeptide 1a-2c
was synthesized following the General Peptide Synthesis procedure,
utilizing 1100 mg (5.06 mmol, 1.1 equiv) of amine 1a, 1000 mg
(4.6 mmol, 1.0 equiv) of acid 2c, 3.2 mL (4 equiv) of DIPEA, and
1630 mg (5.06 mmol, 1.1 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the dipeptide (1700 mg, 98% yield): Rf 0.5 (EtOAc/Hex 35:65);
1H NMR (200 MHz, CDCl3) δ 1.0 (dd, 6H), 1.5 (s, 9H), 2.2 (sept,
1H), 3.2 (dd, 2H), 3.8 (s, 3H), 4.0 (dd, RH), 5.0 (q, RH), 5.1 (br,
1H), 6.4 (br, 1H), 7.2-7.4 (m, 5H).
1
cycle (5 mg, 11% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (500
MHz, CD3OD) δ 0.6-1.0 (m, 24H), 2.0 (m, 4H), 3.0-3.2 (m, 2H),
3.8 (m, RH), 4.1 (m, RH), 4.2 (m, RH), 4.5 (m, RH), 4.6 (m, RH),
7.2-7.4 (m, 5H); LCMS m/z calcd for C29H45N5O5 (M + 1) 544.34,
found 542.2.
Synthesis of Compound 18. Dipeptide 1a-2c. Dipeptide 1a-2c
was synthesized following the General Peptide Synthesis procedure,
utilizing 600 mg (2.25 mmol, 1.2 equiv) of amine 1a, 500 mg (2.3
mmol, 1.0 equiv) of acid 2c, 1.2 mL (3 equiv) of DIPEA, and 1100
mg (3.45 mmol, 1.5 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the dipeptide (770 mg, 88% yield): Rf 0.5 (EtOAc/Hex 35:65); 1H
NMR (200 MHz, CDCl3) δ 0.8-1.0 (dd, 6H), 1.4 (s, 9H), 2.0-
2.2 (m, 1H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 3.8-4.0 (dd, RH), 4.8-
4.9 (dd, RH), 4.9-5.0 (br, 1H), 6.2-6.3 (br, 1H).
Dipeptide 1a-2c-NH2. Dipeptide 1a-2c-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (566 mg, assume quantitative yield).
Tripeptide 1a-2c-3h. Tripeptide 1a-2c-3h was synthesized
following the General Peptide Synthesis procedure, utilizing 590
mg (2.1 mmol, 1.3 equiv) of amine 1a-2c, 480 mg (1.62 mmol,
1.0 equiv) of acid 3h, 1.13 mL (4 equiv) of DIPEA, 480 mg (1.5
mmol, 0.8 equiv) of TBTU, and 300 mg (0.81 mmol, 0.8 equiv) of
HATU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the tripeptide (730 mg, 81%
Dipeptide 1a-2c-NH2. Dipeptide 1a-2c-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (1250 mg, assume quantitative yield).
Tripeptide 1a-2c-3b. Tripeptide 1a-2c-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 625
mg (2.24 mmol, 1.1 equiv) of amine 1a-2c, 444 mg (2.04 mmol,
1.0 equiv) of acid 13b, 1.4 mL (4 equiv) of DIPEA, and 720 mg
(2.24 mmol, 1.1 equiv) of TBTU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (571 mg, 73% yield): Rf 0.4 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.6 (s, 9H), 2.2-2.4 (sept,
2H), 3.2 (sept, 2H), 3.8 (s, 3H), 4.0 (dd, RH), 4.4 (dd, RH), 5.0 (q,
RH), 5.2 (br, 1H), 6.4-6.6 (br, 2H), 7.2-7.4 (m, 5H).
Tripeptide 1a-2c-3b-NH2. Tripeptide 1a-2c-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (455 mg, assume quantitative yield).
Dipeptide 4f-5d. Dipeptide 4f-5d was synthesized following the
General Peptide Synthesis procedure, utilizing 850 mg (5.06 mmol,
1.1 equiv) of amine 4f, 1000 mg (6 mmol, 1.0 equiv) of acid 5d,
3.21 mL (4 equiv) of DIPEA, and 1620 mg (5.06 mmol, 1.1 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (1400 mg, 92%
1
yield): Rf 0.6 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
0.7-0.9 (dd, 6H), 1.4 (s, 9H), 2.0-2.2 (m, 1H), 2.9-2.2 (m, 2H),
3.5-3.9 (m, 2H), 3.6 (s, 3H), 4.2-4.3 (dd, RH), 4.4-4.6 (dd, RH),
4.7-4.8 (dd, RH), 5.4 (br, 1H), 6.4 (br, 1H), 6.8 (br, 1H), 7.0-7.4
(m, 5H).
Tripeptide 1a-2c-3h-NH2. Tripeptide 1a-2c-3h-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (598 mg, assume quantitative yield).
Dipeptide 4f-5d. Dipeptide 4f-5d was synthesized following the
General Peptide Synthesis procedure, utilizing 920 mg (5.5 mmol,
1.2 equiv) of amine 4f, 1000 mg (4.6 mmol, 1.0 equiv) of acid 5d,
2.4 mL (3 equiv) of DIPEA, and 2210 mg (6.9 mmol, 1.5 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (1440 mg, 94%
yield): Rf 0.5 (EtOAc/Hex 35:65); 1H NMR (500 MHz, CDCl3) δ
0.8-1.0 (dd, 6H), 1.2 (s, 9H), 2.1-2.3 (m, 2H), 3.7 (s, 3H), 3.8-
4.0 (dd, RH), 4.5-4.6 (dd, RH), 5 (br, H), 6.4 (br, H).
J. Org. Chem, Vol. 72, No. 6, 2007 1995

Rodriguez et al.
Dipeptide HO-4f-5d. Dipeptide HO-4f-5d was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1296 mg, 93% yield).
utilizing 353 mg (0.97 mmol, 1.1 equiv) of amine 1a-2c-3f, 279
mg (0.88 mmol, 1.0 equiv) of acid, 0.8 mL (5 equiv) of DIPEA,
156 mg (0.49 mmol, 0.55 equiv) of TBTU, and 185 mg (0.49 mmol,
0.55 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(155 mg, 26% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (500 MHz,
DMSO) δ 0.8-1.0 (m, 21H), 1.4 (s, 9H), 1.5-1.6 (m, 2H), 2.0
(m, 3H), 2.9-3.1 (m, 2H), 3.4 (s, 3H), 3.7-3.9 (m, RH), 4.0 (s,
RH), 4.2 (m, RH), 4.3 (m, RH), 4.4 (m, RH), 6.9 (d, 1H), 7.1-7.3
(m, 5H), 7.6 (d, 1H), 7.8 (d, 1H), 8.1 (d, 1H), 8.4 (d, 1H).
Pentapeptide 1a-2c-3h-4f-5d. Pentapeptide 1a-2c-3h-4f-5d was
synthesized following the General Peptide Synthesis procedure,
utilizing 500 mg (1.09 mmol, 1.1 equiv) of amine 1a-2c-3h, 310
mg (1.0 mmol, 1.0 equiv) of acid 4f-5d, 0.86 mL (5 equiv) of
DIPEA, 190 mg (0.58 mmol, 0.6 equiv) of TBTU, and 370 mg
(1.0 mmol, 1.0 equiv) of HATU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
Macrocycle 1a-2c-3f-4f-5d (Compound 19). Macrocycle 1a-
2c-3f-4f-5d (compound 19) was synthesized following the Mac-
rocyclization procedure, utilizing 184 mg (0.31 mmol, 1.0 equiv)
of linear pentapeptide, 213 µL (4 equiv) of DIPEA, 48.2 mg (0.15
mmol, 0.5 equiv) of TBTU, and 174 mg (0.46 mmol, 1.5 equiv) of
HATU. The crude reaction was purified by reverse phase HPLC
to yield the macrocycle (3 mg, 1.6% yield): Rf 0.5 (EtOAc/Hex
1
pentapeptide (670 mg, 45% yield): Rf 0.5 (EtOAc/Hex 1:1); H
NMR (500 MHz, DMSO-d6) δ 0.7-0.8 (m, 18H), 1.4 (s, 9H), 1.8-
2.0 (br, 3H), 2.9-3.0 (m, 2H), 3.5 (s, 3H), 3.8 (br, RH), 4.2 (br,
RH), 4.3 (br, RH), 4.4 (br, RH), 4.4 (br, 2H), 4.7 (br, RH), 6.8 (br,
1H), 7.1-7.4 (m, 10H), 7.6 (br, 1H), 7.9 (br, 1H), 8.2 (br, 1H), 8.4
(br, 1H).
Macrocycle 1a-2c-3h-4f-5d (Compound 18). Macrocycle 1a-
2c-3h-4f-5d (compound 18) was synthesized following the Mac-
rocyclization procedure, utilizing 130 mg (0.2 mmol, 1.0 equiv) of
linear pentapeptide precursor, 0.2 mL (6 equiv) of DIPEA, 80 mg
(0.25 mmol, 1.2 equiv) of TBTU, 100 mg (0.26 mmol, 1.3 equiv)
of HATU, and 80 mg (0.26 mmol, 1.3 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (10 mg, 8% yield): Rf 0.4 (EtOAc/Hex 1:1); LCMS m/z calcd
for C34H47N5O6 (M + 1) 622.77, found 622.3.
1
1:1); H NMR (500 MHz, CD3OD) δ 0.8-1.2 (m, 24H), 1.2-1.4
(m, 2H), 2.0-2.4 (m, 3H), 3.2 (m, 2H), 4.2 (m, RH), 4.8-5.0 (m,
2RH), 5.2 (m, RH), 5.3 (s, RH), 6.8 (d, 1H), 7.2-7.4 (m, 5H), 7.5
(m, 1H), 7.6 (m, 1H), 7.7 (m, 1H), 7.8 (m, 1H); LCMS m/z calcd
for C28H43N5O5 (M - 1) 527.3, found 527.7.
Synthesis of Compound 20. Deprotected Macrocycle 1a-2c-
3h-4f-5d (compound 20) was synthesized following the Hydroge-
nation procedure, utilizing 6 mg (0.009 mmol, 1.0 equiv) of
protected macrocycle, 10% palladium-carbon (cat. amount). The
crude reaction was purified by reverse phase HPLC to yield the
deprotected macrocycle (0.31 mg, 6% yield); LCMS m/z calcd for
C27H41N5O6 (M + 1) 532.5, found 532.5.
Synthesis of Compound 19. Dipeptide 1a-2c. Dipeptide 1a-2c
was synthesized following the General Peptide Synthesis procedure,
utilizing 1.1 g (5.06 mmol, 1.1 equiv) of amine 11a, 1.0 g (4.60
mmol, 1.0 equiv) of acid, 3.2 mL (4 equiv) of DIPEA, and 1.63 g
(5.06 mmol, 1.1 equiv) of TBTU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
Synthesis of Compound 21. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 1904 mg (8.827 mmol, 1.1 equiv) of amine
1a, 2000 mg (8.022 mmol, 1.0 equiv) of acid 2a, 5,622 µL (4 equiv)
of DIPEA, and 3090 mg (9.627 mmol, 1.2 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (3115 mg, 99% yield): Rf 0.5
1
dipeptide (1.7 g, 98% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR
(200 MHz, CDCl3) δ 0.9-1.0 (m, 6H), 1.5 (s, 9H), 2.1-2.4 (m,
1H), 3.2 (d, 2H), 3.7 (s, 3H), 3.9-4.1 (m, RH), 4.9-5.1 (m, RH),
6.4-6.5 (br, 2H), 7.1-7.4 (m, 5H).
Dipeptide 1a-2c-NH2. Dipeptide 1a-2c-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (1.3 g, 100% yield).
1
(EtOAc/Hex 7:13)’ H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd,
6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0-4.2 (m, RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5
(br, 1H) 7.1-7.4 (m, 5H).
Tripeptide 1a-2c-3f. Tripeptide 1a-2c-3f was synthesized fol-
lowing the General Peptide Synthesis procedure, utilizing 626 mg
(2.25 mmol, 1.1 equiv) of amine 1a-2c, 415 mg (2.04 mmol, 1.0
equiv) of acid, 1.4 mL (4 equiv) of DIPEA, and 720 mg (2.24 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide (900
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (2321 mg, quantitative yield).
Tripeptide 1a-2a-3d. Tripeptide 1a-2a-3d was synthesized
following the General Peptide Synthesis procedure, utilizing 631
mg (2.161 mmol, 1.1 equiv) of amine 1a-2a-NH2, 454 mg (1.962
mmol, 1.0 equiv) of acid 3d, 1400 µL (4 equiv) of DIPEA, 378
mg (1.176 mmol, 0.6 equiv) of TBTU, and 448 mg (1.176 mmol
0.6 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide (822
1
mg, 95% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz,
CDCl3) δ 0.8-1.1 (m, 9H), 1.5 (s, 9H), 1.7-2.0 (m, 2H), 3.0-3.2
(m, 1H), 3.1 (d, 2H), 3.7 (s, 3H), 3.8 (m, RH), 4.2 (m, RH), 4.8
(m, RH), 6.6 (br, 3H), 7.0-7.3-7.5 (m, 5H).
Tripeptide 1a-2c-3f-NH2. Tripeptide 1a-2c-3f-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (706 mg, 100% yield).
1
mg, 83% yield): Rf 0.5 (EtOAc/Hex 2:3); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-1.8 (m, 2H), 2.2-
2.4 (m, 1H), 2.7-2.9 (s, 3H), 3.1-3.2 (d, 2H), 3.7 (s, 3H), 4.0 (m,
RH), 4.3 (m, RH), 4.8 (m, RH), 6.2 (br, 1H), 6.4-6.6 (br, 1H),
7.0-7.4 (m, 5H).
Tripeptide 1a-2a-3d-NH2. Tripeptide 1a-2a-3d-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (649 mg, quantitative yield).
Dipeptide 4f-5d. Dipeptide 4f-5d was synthesized following the
General Peptide Synthesis procedure, utilizing 850 mg (5.01 mmol,
1.1 equiv) of amine 4f, 1.0 g (4.60 mmol, 1.0 equiv) of acid, 3.2
mL (4 equiv) of DIPEA, and 1.63 g (5.06 mmol, 1.1 equiv) of
TBTU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (1.4 g, 92% yield):
1
Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ 1.0-1.2
(m, 12H), 1.5 (s, 9H), 1.8 (s, 1H), 2.1-2.4 (m, 1H), 3.9 (s, 3H),
4.0 (t, RH), 4.7 (t, RH), 5.2 (br, 1H), 6.5 (br, 1H).
Dipeptide 4d-5a. Dipeptide 4d-5a was synthesized following
the General Peptide Synthesis procedure, utilizing 488 mg (2.201
mmol, 1.1 equiv) of amine 4d, 500 mg (2.006 mmol, 1.0 equiv) of
acid 5a, 1400 µL (4 equiv) of DIPEA, and 770 mg (2.399 mmol,
1.2 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide (729
Dipeptide HO-4f-5d. Dipeptide HO-4f-5d was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1.3 g, 97% yield).
Pentapeptide 1a-2c-3f-4f-5d. Pentapeptide 1a-2c-3f-4f-5d was
synthesized following the General Peptide Synthesis procedure,
1
mg, 92% yield): Rf 0.5 (EtOAc/Hex 7:13); H NMR (200 MHz,
CDCl3) δ 0.8-1.0 (m, 6H), 1.1-1.4 (m, 5H), 1.5 (s, 9H), 1.6 (m,
1996 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
6H), 1.7 (m, 4H), 1.9 (b, 1H), 3.7 (s, 3H), 4.0-4.2 (m, RH), 4.5-
4.7 (dd, RH), 4.8-4.9 (br, 1H), 6.3-6.4 (br, 1H).
Dipeptide HO-4d-5a. Dipeptide HO-4d-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (637 mg, 94% yield).
was taken on to the next reaction without further purification or
characterization (1921 mg, 98% yield).
Pentapeptide 1a-2a-3b-4e-5a. Pentapeptide 1a-2a-3b-4e-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 717 mg (1.831 mmol, 1.1 equiv) of amine 1a-2a-3b-NH2,
821 mg (1.661 mmol, 1.0 equiv) of acid HO-4e-5a, 2330 µL (8
equiv) of DIPEA, 267 mg (8.321 mmol, 0.5 equiv) of TBTU, 316
mg (8.321 mmol, 0.5 equiv) of HATU, and 100 mg (3.332 mmol,
0.2 equiv) of DEPBT. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(705 mg, 49% yield): Rf 0.4 (EtOAc/Hex 3:2); 1H NMR (500 MHz,
CDCl3) δ 0.8-1.0 (m, 18H), 1.4 (s, 9H), 1.5-2.0 (m, 12H), 2.1-
2.2 (m, 3H), 3.1-3.2 (m, 2H), 3.7 (s, 3H), 4.2-4.6 (br, 3RH), 4.8
(dd, RH), 5.1 (s, 2H), 5.3 (br, 1H), 6.2-6.6 (br, 3H), 6.9 (br, 3H),
7.1-7.4 (m, 10H).
Macrocycle 1a-2a-3b-4e-5a (Compound 22). Macrocycle 1a-
2a-3b-4e-5a (compound 22) was synthesized following the Mac-
rocyclization procedure, utilizing 613 mg (0.8130 mmol, 1.0 equiv)
of linear pentapeptide, 1140 µL (8 equiv) of DIPEA, 104 mg
(0.3250 mmol, 0.4 equiv) of TBTU, 124 mg (0.3250 mmol, 0.4
equiv) of HATU, and 97 mg (0.3250 mmol, 0.4 equiv) of DEPBT.
The crude reaction was purified by reverse phase HPLC to yield
the macrocycle (10 mg, 2% yield): Rf 0.6 (MeOH/EtOAc 5:19);
1H NMR (500 MHz, CDCl3) δ 0.7-1.2 (m, 18H), 1.4-2.2 (m,
15H), 3.0-3.3 (m, 2H), 3.6-4.6 (m, 5RH), 5.0-5.1 (s, 2H), 6.8
(d, 1H), 7.1-7.4 (m, 10H); LCMS m/z calcd for C40H58N6O7
(M + 1) 735.44, found 736.5.
Pentapeptide 1a-2a-3d-4d-5a. Pentapeptide 1a-2a-3d-4d-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 568 mg (1.401 mmol, 1.1 equiv) of amine 1a-2a-3d-NH2,
489 mg (1.273 mmol, 1.0 equiv) of acid, 1800 µL (8 equiv) of
DIPEA, 339 mg (0.8901 mmol, 0.7 equiv) of HATU, and 190 mg
(0.6402 mmol, 0.5 equiv) of DEPBT. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the pentapeptide (833 mg, 83% yield): Rf 0.6 (EtOAc/Hex 7:3);
1H NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 18H), 1.1-1.3 (m,
11H), 1.4 (s, 9H), 1.5-1.8 (m, 4H), 3.0 (s, 3H), 3.1 (d, 2H), 3.7 (s,
3H), 4.2-4.4 (dd, RH), 4.7-4.8 (dd, RH), 4.9-5.0 (br, 2RH), 5.8-
6.0 (br, 1H), 6.4-6.5 (br, 1H), 6.7 (br, 1H), 7.1-7.3 (m, 5H).
Macrocycle 1a-2a-3d-4d-5a (Compound 21). Macrocycle 1a-
2a-3d-4d-5a (compound 21) was synthesized following the Mac-
rocyclization procedure, utilizing 302 mg (0.4610 mmol, 1.0 equiv)
of linear pentapeptide, 680 µL (8 equiv) of DIPEA, 60 mg (0.1801
mmol, 0.4 equiv) of TBTU, 70 mg (0.1801 mmol, 0.4 equiv) of
HATU, and 55 mg (0.1801 mmol, 0.4 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (24 mg, 9% yield): Rf 0.65 (EtOAc/Hex 3:1); LCMS m/z
calcd for C36H57N5O5 (M + 1) 640.44, found 640.4.
Synthesis of Compound 22. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 1904 mg (8.827 mmol, 1.1 equiv) of amine
1a, 2000 mg (8.022 mmol, 1.0 equiv) of acid 2a, 5622 µL (4 equiv)
of DIPEA, and 3090 mg (9.627 mmol, 1.2 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (3115 mg, 99% yield): Rf 0.5
Synthesis of Compound 23. Macrocycle 1a-2a-3b-4e-5a (Com-
pound 23). Macrocycle 1a-2a-3b-4e-5a (compound 23) was
synthesized utilizing 10 mg (0.0136 mmol, 1.0 equiv) of macro-
cyclic pentapeptide, mg (cat. amount) of 10% palladium-carbon.
The crude reaction was filtered using Celite-545 to yield the
deprotected macrocycle (2 mg, 20% yield): 1H NMR (500 MHz,
CDCl3) δ 0.7-1.2 (m, 18H), 1.4-2.2 (m, 15H), 3.0-3.3 (m, 2H),
3.6-4.6 (m, 5RH), 5.1 (br, 1H), 5.5 (d, 1H), 6.8 (d, 1H), 7.1-7.4
(s, 5H), 7.6-7.8 (dd, 2H), 7.9-8.2 (m, 2H); LCMS m/z calcd for
C32H52N6O5 (M + 1) 601.4, found 601.9.
1
(EtOAc/Hex 7:13); H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd,
6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0-4.2 (m, RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5
(br, 1H) 7.1-7.4 (m, 5H).
Synthesis of Compound 24. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 1904 mg (8.827 mmol, 1.1 equiv) of amine
1a, 2000 mg (8.022 mmol, 1.0 equiv) of acid 2a, 5622 µL (4 equiv)
of DIPEA, and 3090 mg (9.627 mmol, 1.2 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (3115 mg, 99% yield): Rf 0.5
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (2321 mg, quantitative yield).
Tripeptide 1a-2a-3b. Tripeptide 1a-2a-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 380
mg (1.301 mmol, 1.1 equiv) of amine 1a-2a-NH2, 257 mg (1.180
mmol, 1.0 equiv) of acid 3b, 830 µL (4 equiv) of DIPEA, and 455
mg (1.421 mmol, 1.2 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
1
(EtOAc/Hex 7:13); H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd,
6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0-4.2 (m, RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5
(br, 1H) 7.1-7.4 (m, 5H).
1
the tripeptide (539 mg, 92% yield): Rf 0.5 (EtOAc/Hex 1:1); H
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (2321 mg, quantitative yield).
NMR (200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.57 (s, 9H), 1.6-
1.7 (m, 3H), 2.1-2.3 (sept, 1H), 3.1-3.4 (m, 2H), 3.8 (s, 3H),
3.9-4.0 (dd, RH), 4.5 (m, RH), 4.8-5.0 (q, RH), 5.0 (br, 1H), 6.4
(d, 1H), 6.6 (br, 1H), 7.2-7.4 (m, 5H).
Tripeptide 1a-2a-3b. Tripeptide 1a-2a-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 631
mg (2.199 mmol, 1.1 equiv) of amine 1a-2a-NH2, 427 mg (1.899
mmol, 1.0 equiv) of acid 3b, 1400 µL (4 equiv) of DIPEA, and
756 mg (2.399 mmol, 1.2 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
Tripeptide 1a-2a-3b-NH2. Tripeptide 1a-2a-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (425 mg, quantitative yield).
Dipeptide 4e-5a. Dipeptide 4e-5a was synthesized following the
General Peptide Synthesis procedure, utilizing 1460 mg (4.401
mmol, 1.1 equiv) of amine 4e, 1000 mg (4.009 mmol, 1.0 equiv)
of acid 5a, 2800 µL (4 equiv) of DIPEA, 1030 mg (3.210 mmol,
0.8 equiv) of TBTU, and 610 mg (1.601 mmol, 0.4 equiv) of
HATU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (2018 mg, 99%
1
the tripeptide (800 mg, 86% yield): Rf 0.5 (EtOAc/Hex 1:1); H
NMR (200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.57 (s, 9H), 1.6-
1.7 (m, 3H), 2.1-2.3 (sept, 1H), 3.1-3.4 (m, 2H), 3.8 (s, 3H),
3.9-4.0 (dd, RH), 4.5 (m, RH), 4.8-5.0 (q, RH), 5.0 (br, 1H), 6.4
(d, 1H), 6.6 (br, 1H), 7.2-7.4 (m, 5H).
Tripeptide 1a-2a-3b-NH2. Tripeptide 1a-2a-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (744 mg, quantitative yield).
Dipeptide 4a-5b. Dipeptide 4a-5b was synthesized following
the General Peptide Synthesis procedure, utilizing 802 mg (4.401
1
yield): Rf 0.5 (EtOAc/Hex 2:3); H NMR (200 MHz, CDCl3) δ
1.2 (m, 6H), 1.6 (s, 9H), 1.7-2.2 (m, 10H), 3.3 (t, 1H), 3.5 (s,
3H), 4.3(m, RH), 4.6 (dd, RH), 5.3 (s, 2H), 7.4-7.6 (s, 5H).
Dipeptide HO-4e-5a. Dipeptide HO-4e-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
J. Org. Chem, Vol. 72, No. 6, 2007 1997

Rodriguez et al.
mmol, 1.1 equiv) of amine 4a, 1000 mg (4.399 mmol, 1.0 equiv)
of acid 5b, 2800 µL (4 equiv) of DIPEA, and 1545 mg (4.799
mmol, 1.2 equiv) of TBTU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
acid 5g, 2000 µL (4 equiv) of DIPEA, 550 mg (1.70 mmol, 0.6
equiv) of TBTU, and 650 mg (1.70 mmol, 0.6 equiv) of HATU.
The crude reaction was purified by column chromatography (silica
gel, EtOAc/Hex) to yield the dipeptide (1058 mg, 99% yield): Rf
0.7 (EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.8-1.0 (m,
12H), 1.5 (s, 9H), 1.6-1.8 (m, 6H), 2.7 (s, 3H), 3.7 (s, 3H), 4.1
(br, RH), 4.6 (br, RH), 6.2 (br, 1H), 6.4 (br, 1H).
Dipeptide HO-4a-5g. Dipeptide HO-4a-5g was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1022 mg, 99% yield).
1
dipeptide (1210 mg, 85% yield): Rf 0.5 (EtOAc/Hex 7:13); H
NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-
1.8 (m, 6H), 3.7 (s, 3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H),
6.5 (br, 1H).
Dipeptide HO-4a-5b. Dipeptide HO-4a-5b was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1112 mg, 95% yield).
Pentapeptide 1a-2a-3b-4a-5g. Pentapeptide 1a-2a-3b-4a-5g was
synthesized following the General Peptide Synthesis procedure,
utilizing 319 mg (0.81 mmol, 1.1 equiv) of amine 1a-2a-3b-NH2,
276 mg (0.74 mmol, 1.0 equiv) of acid HO-4a-5g, 520 µL (4 equiv)
of DIPEA, 143 mg (0.44 mmol, 0.6 equiv) of TBTU, and 169 mg
(0.44 mmol, 0.6 equiv) of HATU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
Pentapeptide 1a-2a-3b-4a-5b. Pentapeptide 1a-2a-3b-4a-5b was
synthesized following the General Peptide Synthesis procedure,
utilizing 308 mg (0.9151 mmol, 1.1 equiv) of amine 1a-2a-3b-
NH2, 286 mg (0.8310 mmol, 1.0 equiv) of acid HO-4a-5b, 600
µL (4 equiv) of DIPEA, 160 mg (0.4991 mmol, 0.6 equiv) of
TBTU, and 190 mg (0.4991 mmol, 0.6 equiv) of HATU. The crude
reaction was purified by column chromatography (silica gel, EtOAc/
Hex) to yield the pentapeptide (514 mg, 86% yield): Rf 0.6 (EtOAc/
1
pentapeptide (490 mg, 90% yield): Rf 0.6 (EtOAc/Hex 3:1); H
NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.4 (s, 9H), 1.5-
1.7 (m, 9H), 1.9-2.0 (m, 1H), 2.3 (br, 1H), 2.8 (s, 3H), 3.0-3.2
(m, 2H), 3.7 (s, 3H), 4.2 (br, RH), 4.3 (br, RH), 4.4 (m, 2RH), 4.8
(dd, RH), 6.4 (br, 1H), 6.6 (br, 1H), 6.7 (br, 1H), 6.9 (br, 1H),
7.1-7.3 (m, 5H).
1
Hex 7:3); H NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.4
(s, 9H), 1.5-1.8 (m, 4H), 1.9-2.6 (m, 4H), 3.0-3.2 (dd, 2H), 3.7
(s, 3H), 4.2-5.0 (m, 5RH), 5.2 (br, 1H), 6.4-6.8 (br, 3H), 7.0-
7.4 (m, 5H).
Macrocycle 1a-2a-3b-4a-5b (Compound 24). Macrocycle 1a-
2a-3b-4a-5b (compound 24) was synthesized following the Mac-
rocyclization procedure, utilizing 177 mg (0.2930 mmol, 1.0 equiv)
of linear pentapeptide, 400 µL (8 equiv) of DIPEA, 38 mg (0.1210
mmol, 0.4 equiv) of TBTU, 45 mg (0.1210 mmol, 0.4 equiv) of
HATU, and 35 mg (0.1210 mmol, 0.4 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (86 mg, 51% yield): Rf 0.6 (EtOAc/Hex 3:1); 1H NMR (500
MHz, CDCl3) δ 0.6-1.1 (m, 24H), 1.3-2.0 (m, 10H), 2.9-3.1
(m, 2H), 3.6 (m, RH), 3.9 (m, RH), 4.1-4.3 (m, 3RH), 7.1-7.3
(m, 5H); LCMS m/z calcd for C32H51N5O5 (M + 1) 586.39, found
586.2.
Synthesis of Compound 25. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 475.8 mg (2.21 mmol, 1.1 equiv) of amine 1a,
500 mg (2.01 mmol, 1.0 equiv) of acid 2a, 1400 µL (4 equiv) of
DIPEA, and 708.3 mg (2.21 mmol, 1.1 equiv) of TBTU. The crude
reaction was purified by column chromatography (silica gel, EtOAc/
Hex) to yield the dipeptide (779.5 mg, 99% yield): Rf 0.7 (EtOAc/
Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H), 1.5 (s,
9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-4.2 (m,
RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5 (br, 1H) 7.1-
7.4 (m, 5H).
Macrocycle 1a-2a-3b-4a-5g (Compound 25). Macrocycle 1a-
2a-3b-4a-5g (compound 25) was synthesized following the Mac-
rocyclization procedure, utilizing 353 mg (0.57 mmol, 1.0 equiv)
of linear pentapeptide, 800 µL (4 equiv) of DIPEA, 173 mg (0.46
mmol, 0.8 equiv) of HATU, and 68 mg (0.23 mmol, 0.4 equiv) of
DEPBT. The crude reaction was purified by reverse phase HPLC
to yield the macrocycle (31 mg, 10% yield): Rf 0.5 (EtOAc/Hex
1
3:1); H NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.5-1.7
(m, 9H), 2.1 (m, 1H), 2.6 (s, 3H), 3.0-3.2 (m, 2H), 3.9 (m, RH),
4.1 (m, RH), 4.4 (m, RH), 4.6 (dd, RH), 4.8 (m, RH) 5.1 (dd, 1H),
5.6-5.8 (dd, 1H) 6.2-6.4 (br, 1H), 7.0 (d, 1H), 7.1-7.3 (m, 5H);
LCMS m/z calcd for H33H53N5O5 (M + 1) 600.40, found 600.60.
Synthesis of Compound 26. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 475.8 mg (2.21 mmol, 1.1 equiv) of amine 1a,
500 mg (2.01 mmol, 1.0 equiv) of acid 2a, 1400 µL (4 equiv) of
DIPEA, and 708.3 mg (2.21 mmol, 1.1 equiv) of TBTU. The crude
reaction was purified by column chromatography (silica gel, EtOAc/
Hex) to yield the dipeptide (779.5 mg, 99% yield): Rf 0.7 (EtOAc/
Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H), 1.5 (s,
9H), 1.6-1.8 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-4.2 (br,
RH), 4.7-4.8 (m, 1H), 4.8-4.9 (br, RH), 6.5 (br, 1H) 7.1-7.4 (m,
5H).
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (580.9 mg, 100% yield).
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (580.9 mg, 100% yield).
Tripeptide 1a-2a-3b. Tripeptide 1a-2a-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 580.9
mg (1.99 mmol, 1.1 equiv) of amine 1a-2a-NH2, 393.1 mg (1.91
mmol, 1.0 equiv) of acid 3b, 1390 µL (4 equiv) of DIPEA, and
639 mg (1.99 mmol, 1.1 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the tripeptide (890.6 mg, 95% yield): Rf 0.6 (EtOAc/Hex 1:1); 1H
NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.4-
1.6 (m, 3H), 2.0-2.2 (m, 1H), 3.1 (d, 2H), 3.7 (s, 3H), 3.9 (m,
RH), 4.4 (m, RH), 4.8 (m, RH), 5.0 (br, 1H), 6.3 (br, 1H), 6.6 (br,
1H), 7.0-7.3 (m, 5H).
Tripeptide 1a-2a-3b-NH2. Tripeptide 1a-2a-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (709.2 mg, 100% yield).
Dipeptide 4a-5g. Dipeptide 4a-5g was synthesized following
the General Peptide Synthesis procedure, utilizing 570 mg (3.14
mmol, 1.1 equiv) of amine 4a, 700 mg (2.85 mmol, 1.0 equiv) of
Tripeptide 1a-2a-3b. Tripeptide 1a-2a-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 580.9
mg (1.99 mmol, 1.1 equiv) of amine 1a-2a-NH2, 393.1 mg (1.91
mmol, 1.0 equiv) of acid 3b, 1390 µL (4 equiv) of DIPEA, and
639 mg (1.99 mmol, 1.1 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the tripeptide (890.6 mg, 95% yield): Rf 0.6 (EtOAc/Hex 1:1); 1H
NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-
1.7 (m, 3H), 2.0-2.2 (m, 1H), 3.1 (m, 2H), 3.7 (s, 3H), 3.9 (q,
RH), 4.4 (m, RH), 4.8 (m, RH), 5.0 (br, 1H), 6.3 (br, 1H), 6.5 (br,
1H), 7.0-7.3 (m, 5H).
Tripeptide 1a-2a-3b-NH2. Tripeptide 1a-2a-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (709.2 mg, 100% yield).
Dipeptide 4a-5f. Dipeptide 4a-5f was synthesized following the
General Peptide Synthesis procedure, utilizing 528 mg (2.90 mmol,
1.1 equiv) of amine 4a, 500 mg (2.60 mmol, 1.0 equiv) of acid 5f,
1998 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
1850 µL (4 equiv) of DIPEA, and 1018 mg (3.20 mmol, 1.2 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (775.1 mg,
100% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3)
δ 0.8-1.0 (m, 6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0 (s, 3H), 3.7
(s, 3H), 3.8-4.0 (q, 2RH) 4.6 (br, RH), 6.4 (br, 1H).
Dipeptide HO-4a-5f. Dipeptide HO-4a-5f was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (738.7 mg, 100% yield).
MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.5-1.8 (m, 6H),
3.7 (s, 3H), 4.1 (br, RH), 4.6 (br, RH), 4.8 (br, 1H), 6.5 (br, 1H).
Dipeptide HO-4a-5b. Dipeptide HO-4a-5b was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (538 mg, 97% yield).
Pentapeptide 1a-2a-3d-4a-5b. Pentapeptide 1a-2a-3d-4a-5b was
synthesized following the General Peptide Synthesis procedure,
utilizing 453.3 mg (1.12 mmol, 1.1 equiv) of amine 1a-2a-3d-NH2,
352 mg (1.08 mmol, 1.0 equiv) of acid HO-4a-5b, 754 µL (4 equiv)
of DIPEA, 69.4 mg (0.22 mmol, 0.2 equiv) of TBTU, and 410.4
mg (1.08 mmol, 1.0 equiv) of HATU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the pentapeptide (474.3 mg, 60% yield): Rf 0.7 (EtOAc/Hex 3:1);
1H NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.5 (s, 9H), 1.5-
1.7 (m, 9H), 2.3 (br, 1H), 2.9 (s, 3H), 3.1 (m, 2H), 3.7 (s, 3H), 4.1
(m, RH) 4.2 (dd, RH), 4.3 (br, RH), 4.5 (m, RH), 4.8 (dd, RH), 5.5
(br, 1H), 6.6 (br, 1H), 6.6 (br, 1H), 6.8 (br, 1H), 7.1-7.3 (m, 5H).
Macrocycle 1a-2a-3d-4a-5b (Compound 27). Macrocycle 1a-
2a-3d-4a-5b (Compound 27) was synthesized following the Mac-
rocyclization procedure, utilizing 118 mg (0.191 mmol, 1.0 equiv)
of linear pentapeptide, 134 µL (4 equiv) of DIPEA, 31 mg (0.096
mmol, 0.5 equiv) of TBTU, 36 mg (0.096 mmol, 0.5 equiv) of
HATU, and 29 mg (0.096 mmol, 0.5 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
Pentapeptide 1a-2a-3b-4a-5f. Pentapeptide 1a-2a-3b-4a-5f was
synthesized following the General Peptide Synthesis procedure,
utilizing 560 mg (1.43 mmol, 1.1 equiv) of amine 1a-2a-3b-NH2,
369 mg (1.30 mmol, 1.0 equiv) of acid HO-4a-5f, 910 µL (4 equiv)
of DIPEA, 250 mg (0.76 mmol, 0.6 equiv) of TBTU, and 297 mg
(0.76 mmol, 0.6 equiv) of HATU. The crude reaction was purified
by column chromatography (silica gel, EtOAc/Hex) to yield the
1
pentapeptide (660 mg, 88% yield): Rf 0.5 (EtOAc/Hex 3:1); H
NMR (200 MHz, CD3OD) δ 0.9-1.1 (m, 18H), 1.5 (s, 9H), 1.6-
1.7 (m, 6H), 2.1 (m, 1H), 3.0 (s, 3H), 3.1-3.2 (m, 2H), 3.7 (s,
3H), 3.8-4.0 (q, 2RH), 4.1 (m, RH), 4.4 (br, RH), 4.6 (br, RH),
4.7 (t, RH), 7.2-7.4 (m, 5H).
Macrocycle 1a-2a-3b-4a-5f (Compound 26). Macrocycle 1a-
2a-3b-4a-5f (compound 26) was synthesized following the Mac-
rocyclization procedure, utilizing 208 mg (0.37 mmol, 1.0 equiv)
of linear pentapeptide, 260 µL (4 equiv) of DIPEA, 112 mg (0.30
mmol, 0.8 equiv) of HATU, and 44.3 mg (0.15 mmol, 0.4 equiv)
of DEPBT. The crude reaction was purified by reverse phase HPLC
to yield the macrocycle (10 mg, 6.5% yield): Rf 0.4 (EtOAc/Hex
3:1); LCMS m/z calcd for H29H45N5O5 (M + 1) 544.34, found
545.30.
1
cycle (10 mg, 8.42% yield): Rf 0.5 (EtOAc/Hex 3:1); H NMR
(500 MHz, CDCl3) δ 0.8-1.0 (m, 24H), 1.4-1.7 (m, 9H), 2.2 (br,
1H), 3.0-3.2 (dd, 2H), 4.1 (dx, RH), 4.3 (br, RH), 4.4 (m, 2RH),
4.8 (dd, RH), 5.9 (d, 1H), 6.4 (br, 1H), 6.8 (br, 1H), 6.8 (br, 1H),
7.1-7.2 (m, 5H), 7.3 (br, 1H); LCMS m/z calcd for H33H53N5O5
(M + 1) 600.40, found 600.50.
Synthesis of Compound 28. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 1904 mg (8.827 mmol, 1.1 equiv) of amine
1a, 2000 mg (8.022 mmol, 1.0 equiv) of acid 2a, 5622 µL (4 equiv)
of DIPEA, and 3090 mg (9.627 mmol, 1.2 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (3115 mg, 99% yield): Rf 0.5
Synthesis of Compound 27. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 475.8 mg (2.206 mmol, 1.1 equiv) of amine
1a, 500 mg (2.01 mmol, 1.0 equiv) of acid 2a, 1400 µL (4 equiv)
of DIPEA, and 708.3 mg (2.21 mmol, 1.1 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (763.8 mg, 97% yield): Rf 0.7
(EtOAc/Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H),
1.4 (s, 9H), 1.6-1.8 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-
4.2 (br, RH), 4.7-4.8 (br, RH), 4.8-4.9 (m, 1H), 6.5 (br, 1H) 7.1-
7.4 (m, 5H).
1
(EtOAc/Hex 7:13); H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd,
6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0-4.2 (m, RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5
(br, 1H) 7.1-7.4 (m, 5H)
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (2321 mg, quantitative yield).
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (565.2 mg, 100% yield).
Tripeptide 1a-2a-3a. Tripeptide 1a-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 360
mg (1.231 mmol, 1.1 equiv) of amine 1a-2a-NH2, 243 mg (1.121
mmol, 1.0 equiv) of acid 3a, 800 µL (4 equiv) of DIPEA, and 431
mg (1.339 mmol, 1.2 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
Tripeptide 1a-2a-3d. Tripeptide 1a-2a-3d was synthesized
following the General Peptide Synthesis procedure, utilizing 565.2
mg (1.95 mmol, 1.1 equiv) of amine 1a-2a-NH2, 408.2 mg (1.73
mmol, 1.0 equiv) of acid 3d, 1300 µL (4 equiv) of DIPEA, and
626.1 mg (1.95 mmol, 1.1 equiv) of TBTU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the tripeptide (716 mg, 80% yield): Rf 0.6 (EtOAc/Hex
1:1); 1H NMR (200 MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.5 (s, 9H),
1.5-1.7 (m, 3H), 2.2-2.4 (m, 1H), 2.8 (m, 3H), 3.1 (d, 2H), 3.7
(s, 3H), 4.0 (br, RH), 4.4 (br, RH), 4.8 (q, RH), 6.5-6.7 (br, 2H),
7.0-7.3 (m, 5H).
1
the tripeptide (500 mg, 91% yield): Rf 0.5 (EtOAc/Hex 1:1); H
NMR (200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.57 (s, 9H), 1.6-
1.7 (m, 3H), 2.1-2.3 (sept, 1H), 3.1-3.4 (m, 2H), 3.8 (s, 3H),
3.9-4.0 (dd, RH), 4.5 (m, RH), 4.8-5.0 (q, RH), 5.0 (br, 1H), 6.4
(d, 1H), 6.6 (br, 1H), 7.2-7.4 (m, 5H).
Tripeptide 1a-2a-3a-NH2. Tripeptide 1a-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (399 mg, quantitative yield).
Dipeptide 4e-5a. Dipeptide 4e-5a was synthesized following the
General Peptide Synthesis procedure, utilizing 1460 mg (4.401
mmol, 1.1 equiv) of amine 4e, 1000 mg (4.009 mmol, 1.0 equiv)
of acid 5a, 2,800 µL (4 equiv) of DIPEA, 1030 mg (3.210 mmol,
0.8 equiv) of TBTU, and 610 mg (1.601 mmol, 0.4 equiv) of
HATU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (2018 mg, 99%
Tripeptide 1a-2a-3d-NH2. Tripeptide 1a-2a-3d-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (453.3 mg, 100% yield).
Dipeptide 4a-5b. Dipeptide 4a-5b was synthesized following
the General Peptide Synthesis procedure, utilizing 401 mg (2.206
mmol, 1.1 equiv) of amine 4a, 500 mg (2.006 mmol, 1.0 equiv) of
acid 5b, 1400 µL (4 equiv) of DIPEA, and 708.3 mg (2.206 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the dipeptide
1
1
(577.1 mg, 80% yield): Rf 0.7 (EtOAc/Hex 1:1); H NMR (200
yield): Rf 0.5 (EtOAc/Hex 2:3); H NMR (200 MHz, CDCl3) δ
J. Org. Chem, Vol. 72, No. 6, 2007 1999

Rodriguez et al.
1.2 (m, 6H), 1.6 (s, 9H), 1.7-2.2 (m, 10H), 3.3 (t, 1H), 3.5 (s,
3H), 4.3(m, RH), 4.6 (dd, RH), 5.3 (s, 2H), 7.4-7.6 (s, 5H).
Dipeptide HO-4e-5a. Dipeptide HO-4e-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1921 mg, 98% yield).
Dipeptide HO-4e-5a. Dipeptide HO-4e-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (1921 mg, 98% yield).
Pentapeptide 1b-2b-3b-4e-5a. Pentapeptide 1b-2b-3b-4e-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 383 mg (0.9710 mmol, 1.1 equiv) of amine 1b-2b-3b-
NH2, 438 mg (0.8880 mmol, 1.0 equiv) of acid HO-4e-5a, 1250
µL (8 equiv) of DIPEA, 143 mg (0.4441 mmol, 0.5 equiv) of
TBTU, 169 mg (0.4441 mmol, 0.5 equiv) of HATU, and 53 mg
(0.1780 mmol, 0.2 equiv) of DEPBT. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the pentapeptide (325 mg, 42% yield): Rf 0.4 (EtOAc/Hex 3:2);
1H NMR (500 MHz, CDCl3) δ 0.8-1.0 (m, 18H), 1.4 (s, 9H), 1.5-
2.0 (m, 12H), 2.1-2.2 (m, 3H), 3.1-3.2 (m, 2H), 3.7 (s, 3H), 4.2-
4.6 (br, 3RH), 4.8 (q, RH), 5.1 (s, 2H), 5.2-5.4 (br, 2H), 6.1 (br,
1H), 6.7 (br, 1H), 7.0-7.4 (m, 10H) 7.6 (br, 1H).
Pentapeptide 1a-2a-3a-4e-5a. Pentapeptide 1a-2a-3a-4e-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 399 mg (1.021 mmol, 1.1 equiv) of amine 1a-2a-3a-NH2,
458 mg (0.9311 mmol, 1.0 equiv) of acid HO-4e-5a, 1300 µL (8
equiv) of DIPEA, 179 mg (0.5611 mmol, 0.6 equiv) of TBTU,
and 212 mg (0.5611 mmol, 0.6 equiv) of HATU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the pentapeptide (520 mg, 65% yield): Rf 0.4 (EtOAc/
1
Hex 3:2); H NMR (500 MHz, CD3OD) δ 0.8-1.0 (m, 18H), 1.4
(s, 9H), 1.5-1.9 (m, 12H), 2.0-2.1 (m, 3H), 3.0-3.2 (m, 2H), 3.7
(s, 3H), 3.9-4.2 (dd, 3RH), 4.3-4.5 (br, 2H), 4.6 (dd, RH), 5.1 (s,
2H), 5.5 (d, 1H), 7.2-7.4 (m, 10H).
Macrocycle 1b-2b-3b-4e-5a (Compound 29). Macrocycle 1b-
2b-3b-4e-5a (compound 29) was synthesized following the Mac-
rocyclization procedure, utilizing 283 mg (0.3750 mmol, 1.0 equiv)
of linear pentapeptide, 530 µL (8 equiv) of DIPEA, 48 mg (0.1510
mmol, 0.4 equiv) of TBTU, 57 mg (0.1510 mmol, 0.4 equiv) of
HATU, and 45 mg (0.1510 mmol, 0.4 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
Macrocycle 1a-2a-3a-4e-5a (Compound 28). Macrocycle 1a-
2a-3a-4e-5a (compound 28) was synthesized following the Mac-
rocyclization procedure, utilizing 451 mg (0.5990 mmol, 1.0 equiv)
of linear pentapeptide, 840 µL (8 equiv) of DIPEA, 228 mg (0.5990
mmol, 1.0 equiv) of HATU, and 36 mg (0.1190 mmol, 0.2 equiv)
of DEPBT. The crude reaction was purified by reverse phase HPLC
to yield the macrocycle (219 mg, 50% yield): Rf 0.6 (MeOH/EtOAc
1
cycle (54 mg, 20% yield): Rf 0.6 (MeOH/EtOAc 5:19); H NMR
1
(500 MHz, CDCl3) δ 0.7-1.2 (m, 18H), 1.4-2.2 (m, 15H), 3.0-
3.3 (m, 2H), 3.6-4.6 (m, 5RH), 5.0-5.1 (s, 2H), 6.8 (d, 1H), 7.1-
7.4 (m, 10H); LCMS m/z calcd for C40H58N6O7 (M + 1) 735.44,
found 735.8.
5:19); H NMR (500 MHz, CDCl3) δ 0.6-1.2 (m, 18H), 1.3-2.3
(m, 15H), 3.0-3.3 (m, 2H), 3.5-4.6 (m, 5RH), 4.4.7-4.8 (br, 2H),
5.1 (s, 2H), 5.3-5.6 (br, 2H), 7.0-7.4 (m, 10H); LCMS m/z calcd
for C40H58N6O7 (M + 1) 735.44, found 735.5.
Synthesis of Compound 29. Dipeptide 1b-2b. Dipeptide 1b-
2b was synthesized following the General Peptide Synthesis
procedure, utilizing 925 mg (4.412 mmol, 1.1 equiv) of amine 1b,
1000 mg (4.412 mmol, 1.0 equiv) of acid 2b, 2780 µL (4 equiv)
of DIPEA, and 1416 mg (4.412 mmol, 1.1 equiv) of TBTU. The
crude reaction was purified by column chromatography (silica gel,
EtOAc/Hex) to yield the dipeptide (1572 mg, 99% yield): Rf 0.5
Synthesis of Compound 30. Macrocycle 1a-2a-3a-4e-5a (Com-
pound 30). Macrocycle 1a-2a-3a-4e-5a (compound 30) was
synthesized utilizing 10 mg (0.0136 mmol, 1.0 equiv) of macro-
cyclic pentapeptide, mg (cat. amount) of 10% palladium-carbon.
The crude reaction was filtered using Celite-545 to yield the
deprotected macrocycle (8 mg, 80% yield): 1H NMR (500 MHz,
CDCl3) δ 0.7-1.2 (m, 18H), 1.4-2.2 (m, 15H), 3.0-3.3 (m, 2H),
3.6-4.6 (m, 5RH), 5.1 (br, 1H), 5.5 (d, 1H), 6.8 (d, 1H), 7.1-7.4
(s, 5H), 7.6-7.8 (dd, 2H), 7.9-8.2 (m, 2H); LCMS m/z calcd for
C32H52N6O5 (M + 1) 601.4, found 601.1.
Synthesis of Compound 31. Macrocycle 1b-2b-3b-4e-5a
(Compound 31). Macrocycle 1b-2b-3b-4e-5a (compound 31) was
synthesized utilizing 54 mg (0.0717 mmol, 1.0 equiv) of macro-
cyclic pentapeptide, mg (cat. amount) of 10% palladium-carbon.
The crude reaction was filtered using Celite-545 to yield the
deprotected macrocycle (2 mg, 3.7% yield): LCMS m/z calcd for
C32H52N6O5 (M + 1) 601.4, found 601.4.
Synthesis of Compound 32. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 670 mg (3.09 mmol, 1.1 equiv) of amine 1a,
700 mg (2.81 mmol, 1.0 equiv) of acid, 2.0 mL (4 equiv) of DIPEA,
and 1.08 g (3.37 mmol, 1.2 equiv) of TBTU. The crude reaction
was purified by column chromatography (silica gel, EtOAc/Hex)
to yield the dipeptide (1.07 g, 97% yield): Rf 0.5 (EtOAc/Hex 1:1);
1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H), 1.5 (s, 9H), 1.5-
1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-4.2 (m, RH), 4.8-
4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5 (br, 1H) 7.1-7.4 (m, 5H).
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (800 mg, 100% yield).
1
(EtOAc/Hex 7:13); H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd,
6H), 1.5 (s, 9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H),
4.0-4.2 (m, RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5
(br, 1H) 7.1-7.4 (m, 5H).
Dipeptide 1b-2b-NH2. Dipeptide 1b-2b-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (1172 mg, quantitative yield).
Tripeptide 1b-2b-3b. Tripeptide 1b-2b-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 455
mg (1.556 mmol, 1.1 equiv) of amine 1b-2b-NH2, 307 mg (1.414
mmol, 1.0 equiv) of acid 3b, 740 µL (3 equiv) of DIPEA, and 455
mg (1.556 mmol, 1.1 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
1
the tripeptide (640 mg, 92% yield): Rf 0.5 (EtOAc/Hex 1:1); H
NMR (200 MHz, CDCl3) δ 0.9-1.0 (m, 12H), 1.57 (s, 9H), 1.6-
1.7 (m, 3H), 2.1-2.3 (sept, 1H), 3.1-3.4 (m, 2H), 3.8 (s, 3H),
3.9-4.0 (dd, RH), 4.5 (m, RH), 4.8-5.0 (q, RH), 5.0 (br, 1H), 6.4
(d, 1H), 6.6 (br, 1H), 7.2-7.4 (m, 5H).
Tripeptide 1b-2b-3b-NH2. Tripeptide 1b-2b-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (510 mg, quantitative yield).
Dipeptide 4e-5a. Dipeptide 4e-5a was synthesized following the
General Peptide Synthesis procedure, utilizing 1460 mg (4.401
mmol, 1.1 equiv) of amine 4e, 1000 mg (4.009 mmol, 1.0 equiv)
of acid 5a, 2800 µL (4 equiv) of DIPEA, 1030 mg (3.210 mmol,
0.8 equiv) of TBTU, and 610 mg (1.601 mmol, 0.4 equiv) of
HATU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (2018 mg, 99%
Tripeptide 1a-2a-3a. Tripeptide 1a-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 800
mg (2.73 mmol, 1.1 equiv) of amine 1a-2a, 539 mg (2.48 mmol,
1.0 equiv) of acid, 2.3 mL (4 equiv) of DIPEA, 1.29 g (4.0 mmol,
1.2 equiv) of TBTU, and 0.5 equiv (0.5 mmol, 0.15 equiv) of
HATU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the tripeptide (988 mg, 81%
1
yield): Rf 0.5 (EtOAc/Hex 2:3); H NMR (200 MHz, CDCl3) δ
1
1.2 (m, 6H), 1.6 (s, 9H), 1.7-2.2 (m, 10H), 3.3 (t, 1H), 3.5 (s,
3H), 4.3(m, RH), 4.6 (dd, RH), 5.3 (s, 2H), 7.4-7.6 (s, 5H).
yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (500 MHz, CDCl3) δ
0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.4-1.6 (m, 2H), 2.0-2.2 (m, 1H),
2000 J. Org. Chem., Vol. 72, No. 6, 2007

SansalVamide A as a NoVel Antitumor Template
3.1 (d, 2H), 3.7 (s, 3H), 3.8 (m, RH), 4.2 (m, RH), 4.8 (m, RH),
5.0 (br, 1H), 6.2 (br, 1H), 6.3 (br, 1H), 7.0-7.3 (m, 5H).
Tripeptide 1a-2a-3a-NH2. Tripeptide 1a-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (787 mg, 100% yield).
dipeptide was taken on to the next reaction without further
purification or characterization (451 mg, 100% yield).
Dipeptide 4a-5c. Dipeptide 4a-5c was synthesized following the
General Peptide Synthesis procedure, utilizing 602 mg (3.31 mmol,
1.1 equiv) of amine 4a, 750 mg (3.01 mmol, 1.0 equiv) of acid,
2.1 mL (4 equiv) of DIPEA, and 116 mg (3.61 mmol, 1.1 equiv)
of TBTU. The crude reaction was purified by column chromatog-
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (844 mg, 75%
Dipeptide 4c-5a. Dipeptide 4c-5a was synthesized following the
General Peptide Synthesis procedure, utilizing 696 mg (3.55 mmol,
1.1 equiv) of amine 4c, 805 mg (3.23 mmol, 1.0 equiv) of acid,
2.3 mL (4 equiv) of DIPEA, and 1.25 g (3.88 mmol, 1.2 equiv) of
TBTU. The crude reaction was purified by column chromatography
(silica gel, EtOAc/Hex) to yield the dipeptide (1.02 g, 83% yield):
1
yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
0.8-1.0 (m, 6H), 1.4 (s, 9H), 1.5-1.8 (m, 6H), 2.7 (s, 3H), 3.7 (s,
3H), 4.4 (br, RH), 4.7 (br, RH), 6.2 (br, 1H), 6.7 (br, 1H).
Dipeptide HO-4a-5c. Dipeptide HO-4a-5c was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (509 mg, 63% yield).
1
Rf 0.5 (EtOAc/Hex 1:1); H NMR (500 MHz, CDCl3) δ 0.8-1.0
(m, 6H), 1.4 (s, 9H), 1.5-1.8 (m, 6H), 3.0 (s, 3H), 3.7 (s, 3H), 4.4
(br, RH), 4.7 (br, RH), 6.2 (br, 1H), 6.7 (br, 1H).
Dipeptide HO-4c-5a. Dipeptide HO-4c-5a was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (892 mg, 89% yield).
Pentapeptide 1a-2a-3a-4a-5c. Pentapeptide 1a-2a-3a-4a-5c was
synthesized following the General Peptide Synthesis procedure,
utilizing 451 mg (1.15 mmol, 1.1 equiv) of amine 1a-2a-3a, 358
mg (1.05 mmol, 1.0 equiv) of acid, 1.5 mL (8 equiv) of DIPEA,
236 mg (0.74 mmol, 0.7 equiv) of TBTU, and 279 mg (0.74 mmol,
0.7 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(504 mg, 67% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (500 MHz,
CDCl3) δ 0.8-1.0 (m, 24H), 1.5-1.7 (s, 6H), 1.8 (m, 3H), 2.2 (br,
1H), 2.9 (s, 1H), 3.7 (s, 3H), 4.2 (m, RH), 4.3 (br, RH), 4.4 (br,
RH), 4.6 (br, RH), 4.8 (m, RH), 6.2 (s, 1H), 6.6 (s, 1H), 6.7 (s,
1H), 6.9 (s, 1H), 7.1-7.4 (m, 5H); LCMS m/z calcd for C33H55N5O6
(M + 1) 618.82, found 618.4.
Macrocycle 1a-2a-3a-4a-5c (Compound 33). Macrocycle 1a-
2a-3a-4a-5c (compound 33) was synthesized following the Mac-
rocyclization procedure, utilizing 184 mg (0.31 mmol, 1.0 equiv)
of linear pentapeptide, 213 µL (4 equiv) of DIPEA, 48.2 mg (0.15
mmol, 0.5 equiv) of TBTU, and 174 mg (0.46 mmol, 1.5 equiv) of
HATU. The crude reaction was purified by reverse phase HPLC
to yield the macrocycle (3 mg, 1.6% yield): Rf 0.5 (EtOAc/Hex
1:1); LCMS m/z calcd for C33H53N5O5 (M + 1) 600.8, found 600.3.
Synthesis of Compound 34. Dipeptide 1b-2b. Dipeptide 1b-
2b was synthesized following the General Peptide Synthesis
procedure, utilizing 952 mg (4.4 mmol, 1.1 equiv) of amine 1b,
1.0 g (4.0 mmol, 1.0 equiv) of acid, 2.8 mL (4 equiv) of DIPEA,
and 1.4 g (4.4 mmol, 1.1 equiv) of TBTU. The crude reaction was
purified by column chromatography (silica gel, EtOAc/Hex) to yield
the dipeptide (1.5 g, 98% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 1.0-1.1 (dd, 6H), 1.5 (s, 9H), 1.8 (s, 3H),
3.2-3.4 (t, 2H), 3.8 (s, 3H), 4.1-4.3 (br, RH), 4.8-4.9 (m, RH),
4.8-5.0 (br, RH), 6.6 (d, 1H), 7.2-7.4 (m, 5H).
Pentapeptide 1a-2a-3a-4c-5a. Pentapeptide 1a-2a-3a-4c-5a was
synthesized following the General Peptide Synthesis procedure,
utilizing 787 mg (2.01 mmol, 1.1 equiv) of amine 1a-2a-3c, 681
mg (1.82 mmol, 1.0 equiv) of acid, 3.5 mL (4 equiv) of DIPEA,
600 mg (1.74 mmol, 0.95 equiv) of TBTU, and 700 mg (1.74 mmol,
0.95 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(1.74 g, 96% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (500 MHz,
CDCl3) δ 0.8-1.0 (m, 24H), 1.4 (s, 9H), 1.6-1.8 (m, 9H), 2.2 (br,
1H), 2.8 (s, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.2 (m, RH), 4.4
(br, RH), 4.5 (b, RH), 4.8 (dd, RH), 5.0(m, 1H), 6.2 (br, 1H), 6.5
(br, 1H), 6.6 (br, 1H), 6.7 (br, 1H), 7.1-7.3 (m, 5H); LCMS m/z
calcd for C39H65N5O8 (M + 23) 754.48, found 754.4.
Macrocycle 1a-2a-3a-4c-5a (Compound 32). Macrocycle 1a-
2a-3a-4c-5a (compound 32) was synthesized following the Mac-
rocyclization procedure, utilizing 153 mg (0.27 mmol, 1.0 equiv)
of linear pentapeptide, 200 µL (10 equiv) of DIPEA, 40 mg (0.12
mmol, 0.5 equiv) of TBTU, 48 mg (1.24 mmol, 0.5 equiv) of
HATU, and 40 mg (0.12 mmol, 0.5 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (22.3 mg, 14% yield): Rf 0.5 (EtOAc/Hex 1:1); LCMS m/z
calcd for C33H53N5O5 (M + 1) 600.40, found 600.6.
Synthesis of Compound 33. Dipeptide 1a-2a. Dipeptide 1a-
2a was synthesized following the General Peptide Synthesis
procedure, utilizing 476 mg (2.210 mmol, 1.1 equiv) of amine 1a,
500 mg (2.010 mmol, 1.0 equiv) of acid, 1.4 mL (4 equiv) of
DIPEA, and 774 mg (2.410 mmol, 1.1 equiv) of TBTU. The crude
reaction was purified by column chromatography (silica gel, EtOAc/
Hex) to yield the dipeptide (647 mg, 82% yield): Rf 0.5 (EtOAc/
Hex 1:1); 1H NMR (200 MHz, CDCl3) δ 0.9-1.0 (dd, 6H), 1.5 (s,
9H), 1.5-1.7 (m, 3H), 3.0-3.2 (m, 2H), 3.7 (s, 3H), 4.0-4.2 (m,
RH), 4.8-4.9 (m, RH), 4.7-4.9 (br, 1H), 6.4-6.5 (br, 1H) 7.1-
7.4 (m, 5H).
Dipeptide 1b-2b-NH2. Dipeptide 1b-2b-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (1.1 g, 100% yield).
Tripeptide 1b-2b-3b. Tripeptide 1b-2b-3b was synthesized
following the General Peptide Synthesis procedure, utilizing 578
mg (2.0 mmol, 1.1 equiv) of amine 1b-2b, 390 mg (1.8 mmol, 1.0
equiv) of acid, 1.25 mL (4 equiv) of DIPEA, and 634 mg (2.0 mmol,
1.1 equiv) of TBTU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the tripeptide (850
Dipeptide 1a-2a-NH2. Dipeptide 1a-2a-NH2 was synthesized
following the General Amine Deprotection procedure. This dipep-
tide was taken on to the next reaction without further purification
or characterization (483 mg, 100% yield).
1
mg, 96% yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz,
Tripeptide 1a-2a-3a. Tripeptide 1a-2a-3a was synthesized
following the General Peptide Synthesis procedure, utilizing 483
mg (1.648 mmol, 1.1 equiv) of amine 1a-2a, 325 mg (1.498 mmol,
1.0 equiv) of acid, 1.0 mL (4 equiv) of DIPEA, and 529 mg (1.648
mmol, 1.1 equiv) of TBTU. The crude reaction was purified by
column chromatography (silica gel, EtOAc/Hex) to yield the
tripeptide (568 mg, 77% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR
(200 MHz, CDCl3) δ 0.8-1.0 (m, 12H), 1.4 (s, 9H), 1.4-1.6 (m,
2H), 2.0-2.2 (m, 1H), 3.1 (d, 2H), 3.7 (s, 3H), 3.8 (m, RH), 4.2
(m, RH), 4.8 (m, RH), 5.0 (br, 1H), 6.2 (br, 1H), 6.3 (br, 1H), 7.0-
7.3 (m, 5H).
CDCl3) δ 0.9-1.1 (d, 12H), 1.5 (s, 9H), 1.7-1.9 (m, 3H), 3.2 (d,
2H), 3.8 (s, 3H), 4.0 (br, RH), 4.5 (br, RH), 4.9 (dd, RH), 5.1 (d,
1H), 6.4 (d, 1H), 7.2-7.4 (m, 5H).
Tripeptide 1b-2b-3b-NH2. Tripeptide 1b-2b-3b-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
dipeptide was taken on to the next reaction without further
purification or characterization (693 mg, 100% yield).
Dipeptide 4b-5d. Dipeptide 4b-5d was synthesized following
the General Peptide Synthesis procedure, utilizing 407 mg (2.2
mmol, 1.1 equiv) of amine 4b, 500 mg (2.0 mmol, 1.0 equiv) of
acid, 1.4 mL (4 equiv) of DIPEA, and 720 mg (2.0 mmol, 1.1 equiv)
of TBTU. The crude reaction was purified by column chromatog-
Tripeptide 1a-2a-3a-NH2. Tripeptide 1a-2a-3a-NH2 was syn-
thesized following the General Amine Deprotection procedure. This
J. Org. Chem, Vol. 72, No. 6, 2007 2001

Rodriguez et al.
raphy (silica gel, EtOAc/Hex) to yield the dipeptide (760 mg, 99%
yield): Rf 0.5 (EtOAc/Hex 1:1); H NMR (200 MHz, CDCl3) δ
HATU, and 54 mg (0.18 mmol, 0.55 equiv) of DEPBT. The crude
reaction was purified by reverse phase HPLC to yield the macro-
cycle (40 mg, 21% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (500
MHz, CD3OD) δ 0.9-1.1 (m, 24H), 1.5-1.7 (m, 9H), 2.0 (dd,
1H), 3.0 (m, 2H), 3.2 (m, RH), 4.0 (br, RH), 4.3 (m, RH), 4.5 (m,
1H), 4.6 (m, RH), 5.0 (t, 1H), 7.2-7.3 (m, 5H), 7.6 (m, 1H); LCMS
m/z calcd for C33H53N5O5 (M + 1) 600.40, found 600.4.
1
1.0-1.1 (m, 12H), 1.5 (s, 9H), 1.6-1.8 (m, 6H), 2.8 (s, 3H), 3.8
(s, 3H), 4.6-4.8 (br, RH).
Dipeptide HO-4b-5d. Dipeptide HO-4b-5d was synthesized
following the General Acid Deprotection procedure. This dipeptide
was taken on to the next reaction without further purification or
characterization (700 mg, 97% yield).
Acknowledgment. We thank the NIH/MARC (5T34GM-
08303) program for support of R.R. (2005/2006). We thank
Pfizer, La Jolla, for equipment and financial donations as well
as their fellowships to T.J.S. (SDSU-Pfizer summer 2005, and
Pfizer SURF 2006). We thank the Howell Foundation for
support for T.J.S. (Spring 2006) and E.P. (Spring 2005). We
thank the NIH/NIGMS-MBRS-IMSD program for support of
J.C. (Spring 2005-Spring 2006 NIH-5R25GM58906) and the
U.S. Coast Guard for support of J.D.B. (2004-2006). We thank
San Diego State University for financial support. S.R.M. was
supported by NIH (AI058241-01).
Pentapeptide 1b-2b-3b-4b-5d. Pentapeptide 1b-2b-3b-4b-5d
was synthesized following the General Peptide Synthesis procedure,
utilizing 346 mg (0.88 mmol, 1.1 equiv) of amine 1b-2b-3b, 290
mg (0.80 mmol, 1.0 equiv) of acid, 0.7 mL (5 equiv) of DIPEA,
142 mg (0.44 mmol, 0.55 equiv) of TBTU, and 172 mg (0.44 mmol,
0.55 equiv) of HATU. The crude reaction was purified by column
chromatography (silica gel, EtOAc/Hex) to yield the pentapeptide
(500 mg, 85% yield): Rf 0.5 (EtOAc/Hex 1:1); 1H NMR (500 MHz,
CDCl3) δ 0.8-1.0 (m, 24H), 1.5 (s, 9H), 1.6-1.7 (m, 9H), 2.2-
2.4 (br, 1H), 2.7 (s, 3H), 3.1-3.2 (m, 2H), 3.2 (d, RH), 3.7 (s,
3H), 4.2 (m, RH), 4.5 (br, RH), 4.8 (m, RH), 6.6-6.7 (br, 1H),
6.8-7.0 (br, 1H), 7.1-7.4 (m, 5H).
Macrocycle 1b-2b-3b-4b-5d (Compound 34). Macrocycle 1b-
2b-3b-4b-5d (compound 34) was synthesized following the Mac-
rocyclization procedure, utilizing 202 mg (0.32 mmol, 1.0 equiv)
of linear pentapeptide, 0.34 mL (6 equiv) of DIPEA, 58 mg (0.18
mmol, 0.55 equiv) of TBTU, 69 mg (0.18 mmol, 0.55 equiv) of
Supporting Information Available: Data for compounds and
their intermediates. This material is available free of charge via
the Internet at http://pubs.acs.org.
JO061830J
2002 J. Org. Chem., Vol. 72, No. 6, 2007