Synthetic studies on nucleoside-type muraymycins antibiotics based on the use of sulfur ylides. Synthesis of bioactive 5′-epimuraymycin analogues

Article abstract of DOI:10.1016/j.tet.2005.09.086

A new synthetic approach to the 5-epimers of muraymycins, a family of complex nucleoside-type antibiotics, is reported based on the synthesis of epoxy amides obtained via the reaction of sulfur ylides with the uridyl aldehyde derivatives 16, 29 and 30, fo

Full text of DOI:10.1016/j.tet.2005.09.086

Tetrahedron 61 (2005) 11850–11865
Synthetic studies on nucleoside-type muraymycins antibiotics
based on the use of sulfur ylides. Synthesis of bioactive
50-epimuraymycin analogues
*
´
Francisco Sarabia and Laura Martın-Ortiz
Department of Biochemistry, Molecular Biology and Organic Chemistry, Faculty of Sciences, University of Malaga, 29071 Malaga, Spain
Received 25 July 2005; revised 19 September 2005; accepted 20 September 2005
Available online 25 October 2005
Abstract—A new synthetic approach to the 5-epimers of muraymycins, a family of complex nucleoside-type antibiotics, is reported based
on the synthesis of epoxy amides obtained via the reaction of sulfur ylides with the uridyl aldehyde derivatives 16, 29 and 30, followed by a
subsequent oxirane ring opening reaction with diamines. This new strategy offers an excellent opportunity for the preparation of muraymycin
analogues of biological interest. In fact, biological studies have revealed these 50-epimers to be as biologically potent as the natural
antibiotics, aside of representing a convergent and flexible route towards the natural congeners.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
the amino sugar (group R2) or in the lipidic side chain
contained in one of the amino acid residues (group R1).
The search and discovery of new antibiotics with novel
mechanisms of action is of great importance in chemical,
biological and clinical circles due to the growing
appearance of drug resistant bacterial strains.1 Among
these new antibiotics, the group composed of the uridyl
lipopeptide antibiotics,2 that include mureidomycins,3
pacidamycins,4 napsamycins,5 liposidomycins,6 FR-9004937
and caprazamycins,8 are of special interest due to their
intriguing mechanism of action, characterized by the
inhibition of the phospho-N-acetyl-muramoyl-pentapep-
tide-transferase (MraY),9 also known as translocase I, an
enzyme responsible for the biosynthesis of the cell-wall of
bacteria. Recently, the muraymycins,10 another group of
nucleoside-lipopeptide antibiotics, have been discovered,
isolated and recognized as inhibitors of MraY, displaying
in vitro and in vivo activities against Gram-positive bacteria
comparable to liposidomycin C and mureidomycin A.11
Coupled with their prominent biological properties, the
muraymycins reveal an attractive molecular architecture,
characterized by an unusual nucleotide disaccharide and an
unprecedented peptidic chain. So far, 19 different members
of the muraymycins have been isolated and identified,
among which the selected compounds 1–5 are depicted in
Figure 1.12 The various muraymycin compounds differ in
Recent synthetic studies of the muraymycins have demon-
strated that truncated derivatives, in which, the 50-amino
ribose sugar moiety and the lipophilic side chain were
removed, and, in addition, the cyclic arginine amino acid
residue was replaced by arginine, were as active as the
natural congeners against Gram positive bacteria. More-
over, the authors demonstrated that the 50-epimer deriva-
tives 7–12 (Fig. 2) showed a biological activity comparable
to the natural congeners.13 In this synthetic study, the
construction of the muraymycin structural core was
efficiently accomplished by an aldolic reaction between
the lithium enolate of dibenzylglycine tert-butyl ester and
the uridyl-50 aldehyde 16.14 Other synthetic contributions to
this family of antibiotics include semisynthesis of ana-
logues15 and the preparation of the unusual cyclic guanidine
amino acid residue,16 named capreomycidine, which is
present not only in the muraymycins, but also in other
natural products such as the capreomycin-type antibiotics.17
Recently, we reported a stereoselective synthetic approach
to liposidomycin antibiotics based on the use of sulfur
ylides.18 According to this methodology, epoxy amide 13
was efficiently prepared and transformed into the diazepa-
none derivative 14 through an indole epoxy amide
intermediate, obtained by oxidation of the indoline ring
with DDQ,19 followed by treatment with diamines (strategy
a). In contrast, the reaction of epoxy amide 13 with diamines
would provide the corresponding amino alcohols 15 in
Keywords: Muraymycins; Complex nucleoside antibiotics; Epoxy amides;
Sulfur ylides.
*
Corresponding author. Tel.: C34 952 134258; fax: C34 952 131941;
e-mail: frsarabia@uma.es
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.09.086

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11851
Figure 2. Molecular structures of representative muraymycins analogues
and antibiotics properties.
75% yield (see Table 1 for details). With the objective of
designing a synthetic route capable of reaching so the
natural muraymycins as the bioactive 50-epimer derivatives,
we proceeded with the construction of the peptidyl chain
linkage. To this aim, we focused on the product 15h,
prepared directly by reaction of 13 with 1,3-propanedia-
mine, or by the Z-cleavage22 of the opening product 15c,
which contained the requisite diamine present in the natural
muraymycins. Thus, the coupling of 15h with the aminoacid
derivative Cbz-Leu-OH23 was accomplished by the action
of the coupling reagent EDCI/HOBt24 that afforded
compound 18. Having incorporated the L-leucine residue,
the access to bioactive muraymycin analogues as depicted
in Figure 2, required the transformation of the indoline
amide to the corresponding ester, for which the oxidation to
the indole derivative was attempted. Unfortunately, this
oxidation did not yield the desired product, resulting in
either decomposition products, when DDQ was used, or the
recovery of starting material when milder oxidation
conditions were used by the action of chloroanil25
(Scheme 2). On the other hand, the cleavage of the Cbz
group was efficiently accomplished, by the action of
hydrogen, to obtain amine 19 in good yield (70%). In
order to give access to unprotected derivatives, the PMB
deprotection constituted a key step. Thus, treatment of
amide 19 with CAN,26 however, failed in the formation of
the desired unprotected derivative. In contrast, the acetal
cleavage mediated by the action of trifluoroacetic acid in
Figure 1. Molecular structures of muraymycins A1, A2, A3, B1 and B2.
a regioselective manner,20 as a straightforward and
convergent approach towards either the 50-epimers of
muraymycins or the natural members, requiring in this
case, an epimerization process at this position (strategy b)
(Scheme 1). Furthermore, this synthetic strategy has the
potential of delivering further structural variations, allowing
entry into a variety of muraymycin analogues via
modifications of the amine nucleophile, which is introduced
in the oxirane ring opening step.
2. Results and discussion
These synthetic studies were initiated with the reaction of
epoxy amide 13 (Scheme 2), readily prepared by conden-
sation of aldehyde 16 with the sulfur ylide, in situ generated
from sulfonium salt 17,18 with different nitrogen nucleo-
philes including sodium azide, allylamine, and various
diamines such as N-Z-1,3-propanediamine,21 which furn-
ished the corresponding oxirane ring opening products
15a–j in good to excellent yields (62–96%) and complete
regioselectivity, with the exception of reaction with
N-methyl-1,3-propanodiamine, in which a 1:1 unseparable
mixture of isomers 15f and 15f0 was obtained in a combined

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11852
Scheme 1. Synthetic strategy towards the liposidomycin and the
muraymycin antibiotics.
Scheme 2. Reagents and conditions: (a) 1.1 equiv 17, 1.1 equiv 20%
NaOH, CH2Cl2/H2O, 0 8C, 2.5 h, 78%; (b) See Table 1 for conditions and
yields; (c) 5.5 equiv NHC4 HCOOK, Pd–C, MeOH, reflux, 2 h, 65%;
(d) 1.0 equiv 15h, 1.2 equiv Cbz-Leu-OH, 1.2 equiv EDCI, 1.2 equiv
HOBt, CH2Cl2, 25 8C, 2 h, 92%; (e) H2, Pd–C, MeOH, 25 8C, 0.5 h, 70%;
(f) TFA/H2O, 0 8C, 1.5 h, 75%.
the presence of H2O proved to be efficient to give triol
derivative 20 in form of its ammonium salt.
With respect to the indoline amide oxidation, these fruitless,
although not surprising,27 results forced us to adopt a second
strategy, initiated with the DDQ oxidation of the indoline
epoxy amide 13 that provided indole epoxy amide 21 in a
76% yield (Scheme 3).18 Having secured the formation of
the indole amide, we proceeded with the reaction of 21 with
N,N-dimethyl amine providing the corresponding N,N-
dimethyl amide 22 (66%) together with its N,N-dimethyl-
amino oxirane ring opening product in a 19% yield. On the
other hand, the preparation of bulky esters, such as the
isopropyl ester 24, was not possible in a straightforward
manner from indole epoxy amide 21, requiring an additional
transesterification step, from its corresponding methyl ester
23 intermediate, by the catalytic action of di-n-butyltin
oxide.28 The oxirane ring opening process with N-Z-1,3-
propanediamine of epoxy amide 22 afforded amino alcohol
25 albeit in a modest 33% yield after a long reaction time
(8 days at reflux). Taking into account that steric hindrance
of the N-Z-1,3-propanediamine could justify the required
long reaction time for completion, which might promote
secondary processes, we decided to carry out these reactions
with 1,3-propanodiamine. In fact, compounds 22 and 24
smoothly reacted with this diamine in 48 h, although with
different results for each case. Thus, for epoxy amide 22, the
desired product 26 was cleanly obtained, according to its 1H
NMR spectra, not requiring further purification, in contrast
to the reaction of epoxy ester 24 that yielded a complex
Table 1. Reaction of epoxy amide 13 with nitrogen nucleophiles
Entry
1
X
Conditions
Yield (%)
N3
AcOH/DMF, 65 8C,
12 h
MeOH, reflux, 12 h
15a (65%)
2
3
4
5
6
NHCH2CH]CH2
NH(CH2)3NHCbz
NMe(CH2)3NHMe
NMe(CH2)2NHMe
NMe(CH2)3NH2C
NH(CH2)3NHMe
NEt(CH2)3NHEt
NH(CH2)3NH2
15b (96%)
MeOH, reflux, 4 days 15c (83%)
MeOH, reflux, 24 h
MeOH, reflux, 24 h
MeOH, reflux, 24 h
15d (81%)
15e (79%)
15fC15f0
(75%)
7
8
9
10
MeOH, reflux, 8 days 15g (66%)
MeOH, reflux, 30 h
MeOH, reflux, 24 h
NHCH2CH(OH)CH2NH2 MeCN, reflux, 24 h
15h (73%)
15i (62%)
15j (69%)
NH(CH2)4NH2
mixture of products, isolating a 1:1 unseparable mixture of
compounds 27a:27b among them. In the light of these
results, we opted to continue with N,N-dimethyl amide 26,
which was coupled with the L-leucine aminoacid derivative,
under similar conditions as described above for compound
18, to obtain compound 28 in a modest yield (36% overall
yield from 22).
In pursuit of circumventing all the synthetic obstacles
associated with the presence of the PMB protecting group
and the indoline-type amide and their subsequent cleavages,
as it has been described above, we chose aldehydes 2929

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11853
Scheme 3. Reagents and conditions: (a) 5.0 equiv DDQ, C6H6, reflux, 24 h,
76%; (b) 1.3 equiv Me2NH, THF, 25 8C, 5 h, 66% of 22, plus a 19% yield of
the N,N-dimethylamino opening product; (c) 1.0 equiv Et3N, MeOH, 25 8C,
0.5 h, 99% for 23; (d) 0.1 equiv nBu2SnO, iPrOH, reflux, 12 h, 67%; (e) 1.0
equiv 22; 1.4 equiv H2N(CH2)3NHCbz, MeOH, reflux, 8 days, 33% for 25;
(f) 2.0 equiv H2N(CH2)3NH2, MeOH, reflux, 48 h, no purification required
for 26, complex mixture for reaction of 24, containing 27a and 27b; (g) 1.0
equiv 26; 1.2 equiv Cbz-Leu-OH, 1.2 equiv EDCI, 1.2 equiv HOBt,
CH2Cl2, 25 8C, 4 h, 36% from 22.
Scheme 4. Reagents and conditions: (a) (i) 1.03 equiv 31, 3.2 equiv NaH,
CH3CN, 0 8C, 3 h, then addition over a solution of 29, CH2Cl2, 0 8C, 2.5 h,
43% for 32; (ii) 1.1 equiv 31, 1.1 equiv 20% NaOH, 1.0 equiv 30, CH2Cl2/
H2O, 0 8C, 1.5 h, 61% for 33; (b) (i) 1.0 equiv 32 1-azido-3-propanoamine,
MeOH, 70 8C, 72 h, 48% for 34; (ii) 1.0 equiv 33 2.1 equiv 1-azido-3-
propanoamine, MeOH, 70 8C, 48 h, 83% for 35; (iii) 1.0 equiv 33 2.0 equiv
1-N-Z-1,3-propanodiamine, MeOH, reflux, 48 h, 83% for 36. (c) 4.0 equiv
and 3030 as starting points and 1-azido-3-propanoamine31 as
nucleophile in the subsequent oxirane ring opening reaction
of the resulting epoxy amides (Scheme 4). Thus, aldehydes
29 and 30, prepared from their corresponding alcohols by
oxidation with DMP32 and IBX,33 respectively, were
reacted with the sulfur ylide derived from the sulfonium
salt 31, to obtain epoxy amides 32 and 33 according to the
one- and two-phases methodologies34 in modest 43 and 61%
yields, respectively, and high stereoselectivities. The
installation of the 1,3-propanediamine linker, required for
the construction of the peptidic chain, was undertaken
through the reaction of epoxy amides 32 and 33 with
1-azido-3-propanoamine to obtain azido alcohols 34 and 35
in 48 and 83% yields, respectively. In a similar way, the
reaction of 33 with N-Z-1,3-propanediamine afforded
opening product 36 in a 83% yield. Either from 35 as
from 36, the amine 37 was obtained in very good yields, by
treatments with triphenylphosphine or ammonium formate
in the presence of palladium. The coupling with the
L-leucine derivative produced amide 38, without further
difficulties, and was converted into amino alcohol 39 by
Z-cleavage mediated by hydrogen. This product represents
an interesting analogue related to the highly bioactive
compound 11 (see Fig. 2). Having failed to oxidize indoline
Ph3P, THF, 25 8C, 1 h, then H2O, 5 h, 75%; (d) Excess of NHC4 HCOOK
,
Pd–C, EtOH, 25 8C, 0.5 h, 72%; (e) 1.0 equiv 37, 1.3 equiv Cbz-Leu-OH,
1.3 equiv EDCI, 1.3 equiv HOBt, CH2Cl2, 25 8C, 6 h, 74%; (f) H2, Pd–C,
MeOH, 25 8C, 0.5 h, 86%; (g) 1.0 equiv 33 5.0 equiv DDQ, C6H6, 80 8C,
24 h, 86%; (h) 2.0 equiv LiOH, THF/H2O, 0 8C, 20 min, 83%; (i) 2.0 equiv
Cl3CC(]NH)OtBu, CH2Cl2, 25 8C, 24 h, 98%; (j) (i) 1.5 equiv 1-azido-3-
propanoamine, MeOH, 70 8C, 96 h, 20% for 43; (ii) 2.0 equiv NaN3, DMF,
65 8C, 3 h, 83% for 44.
amides, containing N-Z-peptidic residues, to the corre-
sponding indole amides, according to precedent results from
our laboratories,27 we then proceeded to investigate the
possibility of fulfilling this oxidation from compounds 34
and 35. However, the DDQ treatments of these indoline
amides failed again to produce the desired indole amides,
leading instead to a complex mixture of decomposition
products. These discouraging results forced us to the
accomplishment of such oxidation in earlier steps. Thus,
epoxy amide 33 was transformed into the epoxy indole
amide 40 by the action of DDQ, followed by basic
hydrolysis with LiOH to obtain acid 41. The formation of

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11854
the tert-butyl ester 42 was carried out by reaction of 41 with
the corresponding tert-butyl trichloroacetimidate35 to
obtain the tert-butyl ester 42 in almost quantitative yield.
With this ester in hand, we proceeded with the introduction
of the diamine linker by reaction with 1-azido-3-aminopro-
pane, expecting no interferences with the ester function, as it
was observed for the isopropyl ester, described above.
Unfortunately, this opening reaction proceeded in a low
20% yield in the formation of 43, in contrast to the reaction
of 42 with simple nucleophiles, such as sodium azide, which
resulted in the formation of the 2-azido opening product 44
in a 83% yield (Scheme 4).
amine 49 in refluxing MeOH, despite the long time reaction
that was required for almost completion (71% convesrion). In
a similar way, trans epoxy amide33was treated with amine 49
to obtain 51 in a 99% yield (79% conversion) (Scheme 5).
3. Conclusions
In conclusion, we have described a new and convergent
synthetic approach towards the 50-epimuraymycins, based
on the use of epoxy amides, which are readily prepared by
the reaction of aldehydes with stabilized sulfur ylides. An
inspection of the structural features present in the
muraymycins reveals the intriguing possibility of applying
an oxirane ring opening reaction to construct modified
50-epimuraymycins of biological interest. These preliminary
synthetic results are of notable importance for the design of
new muraymycin-type antibiotics and for the establishment
of an efficient strategy for the eventual total synthesis of
these natural complex nucleosides, that required the
epimeri0zation at C-50 and the incorporation at this position
of the 5 -aminoribose residue contained in these compounds
by a glycosylation reaction. Whereas the epimerization at
C-5 was successfully achieved via a trans-cis epoxy amide
isomerization, the glycosylation reaction is divised as a
much more difficult synthetic task,39 in which we are
currently devoting our synthetic efforts.
Despite that the 50-epimers of truncated muraymycin
analogues were as active as the derivatives with the right
configuration at this position, we were strongly interested in
the preparation of the 50-(S) analogues in case of an eventual
total synthesis of the natural congeners. From the anti amino
alcohol derivative 15c, we attempted the isomerization at
C-50 position by application of different methodologies
described in the literature,36 but, unfortunately, all these
attempts failed. Finally, according to previous studies in our
laboratories concerning with isomerization of trans epoxy
amides,37 we decided to undertake this epimerization from
epoxy amide 33 by conversion to its corresponding cis
isomer 48, through bromohydrine intermediate. Thus, anti
bromohydrine 45, obtained by treatment of epoxy amide
33 with sodium bromide in the presence of amberlyst-15,38
was subjected to the action of Dess–Martin periodinane to
obtain ketone 46, which was reduced with sodium
borohydride to provide syn bromohydrine 47. Finally,
exposure of 47 to catalytic amounts of sodium methoxide
in methanol afforded cis epoxy amide 48 in a 40% yield over
four steps from 33. With the requisite stereochemistry
contained in the key precursor 48, we devised the
introduction of the peptidic chain in one step by reaction of
epoxy amide 48 with amine 49. Pleasingly, opening product
50 was obtained in excellent yield when 48 was treated with
4. Experimental
4.1. General techniques
All reactions were carried out under an argon atmosphere
with dry, freshly distilled solvents under anhydrous
conditions, unless otherwise noted. Tetrahydrofuran (THF)
and ethyl ether (ether) were distilled from sodium
benzophenone, and methylene chloride (CH2Cl2), benzene
(PhH), and toluene from calcium hydride. Yields refer to
chromatographically and spectroscopically (1H NMR)
homogeneous materials, unless otherwise stated. All
solutions used in workup procedures were saturated unless
otherwise noted. All reagents were purchased at highest
commercial quality and used without further purification
unless otherwise stated.
All reactions were monitored by thin-layer chromatography
carried out on 0.25 mm E. Merck silica gel plates (60F-254)
using UV light as visualizing agent and 7% ethanolic
phosphomolybdic acid or p-anisaldehyde solution and heat
as developing agents. E. Merck silica gel (60, particle size
0.040–0.063 mm) was used for flash column chromatog-
raphy. Preparative thin-layer chromatography (PTLC)
separations were carried out on 0.25, 0.50 or 1 mm E.
Merck silica gel plates (60F-254).
NMR spectra were recorded on a Bruker Avance-400
instrument and calibrated using residual undeuterated solvent
as an internal reference. The following abbreviations were
used to explain the multiplicities: s, singlet; d, doublet; t,
triplet; q, quartet; m, multiplet; band, several overlapping
signals; b, broad. Optical rotations were recorded on a
Perkin-Elmer 241 polarimeter. High-resolution mass spectra
Scheme 5. Reagents and conditions: (a) 4.0 equiv NaBr, Amberlyst-15,
acetone, K20 8C, 12 h, 99%; (b) 2.0 equiv DMP, CH2Cl2, 0 8C, 8 h;
(c) 1.0 equiv NaBH4, EtOH, 0 8C, 1.25 h, 38% over two steps; (d) 3.0 equiv
NaOMe, MeOH, 25 8C, 24 h, 99%; (e) 2.0–4.0 equiv 49, MeOH, 70 8C,
4–14 days, 97% for 50 (71% conversion), 99% for 51 (79% conversion).

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11855
(HRMS) were recorded on a Kratos MS 80 RFA mass
spectrometer under fast atom bombardment (FAB)
conditions.
131.7, 130.9, 128.7, 127.3, 124.7, 124.4, 117.3, 116.5,
114.4, 113.7, 102.5, 93.8, 84.9, 83.2, 81.3, 73.2, 60.5, 55.2,
50.4, 48.0, 43.6, 27.7, 27.3, 25.3; FAB HRMS (NBA): m/e
641.2584, MCNaC calcd for C33H38N4O8 641.2587.
4.2. Opening reactions of epoxy amide 13 with
nucleophiles
4.2.3. Amino alcohol 15c. A solution of N-Z-1,3-
diaminopropane hydrochloride (0.16 g, 0.64 mmol,
1.2 equiv) in MeOH (2 mL) was treated with triethylamine
(0.15 mL, 1.07 mmol, 2.0 equiv) for 30 min at room
temperature. After this time, this solution was added to a
solution of epoxy amide 13 (0.3 g, 0.53 mmol, 1.0 equiv) in
MeOH (3 mL) and the mixture was heated at reflux for
4 days. Then, the mixture was allowed to reach room
temperature and toluene (1.5 mL) was added. The solution
was concentrated under reduced pressure and the crude
product was purified by flash column chromatography
(silica gel, 60% EtOAc, 5% MeOH in hexanes) to provide
amino alcohol 15c (0.34 g, 83%) as a white solid: RfZ0.42
(silica gel, 65% EtOAc, 5% MeOH in hexanes); [a]D22
C36.0 (c 0.1, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.16
(d, JZ8.1 Hz, 1H, Ar indoline), 7.40 (d, JZ8.6 Hz, 2H, Ar
PMB), 7.34–7.27 (m, 6H, aromatics Cbz, H6), 7.14–7.10 (m,
2H, Ar indoline), 7.01 (dd, JZ7.5, 7.5 Hz, 1H, Ar indoline),
6.78 (d, JZ8.6 Hz, 2H, Ar PMB), 5.78 (d, JZ3.2 Hz, 1H,
4.2.1. Azido alcohol 15a. A solution of epoxy amide 13
(0.2 g, 0.356 mmol, 1.0 equiv) in DMF (5 mL) was treated
with sodium azide (93 mg, 1.42 mmol, 4.0 equiv) and acetic
acid (20 mL, 0.356 mmol, 1.0 equiv) and the mixture was
heated at 65 8C. After stirring for 12 h, the solution was
allowed to reach room temperature, diluted with Et2O
(5 mL) and washed with saturated aqueous NH4Cl solution
(5 mL). The aqueous solution was extracted with Et2O (2!
2 mL) and the combined organic phase was washed with
brine (4 mL), dried over MgSO4 and concentrated under
reduced pressure. The crude mixture was purified by flash
column chromatography (silica gel, 60% EtOAc in hexanes)
to provide azido alcohol 15a (0.14 g, 65%) as a white solid:
RfZ0.42 (silica gel, 50% EtOAc in hexanes); [a]2D2 K14.3
(c 0.7, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.14 (d, JZ
8.6 Hz, 1H, Ar indoline), 7.55 (d, JZ8.1 Hz, 1H, H6), 7.41
(d, JZ8.6 Hz, 2H, Ar PMB), 7.12–7.09 (m, 2H, Ar
indoline), 7.04 (dd, JZ7.5, 7.5 Hz, 1H, Ar indoline), 6.79
0
H1 ), 5.69 (d, JZ8.1 Hz, 1H, H5), 5.36 (m, 1H, NHCbz),
0
5.09–4.93 (m, 5H, H3 , CH2ArPMB, CH2ArCbz), 4.83–4.80
0
(d, JZ8.6 Hz, 2H, Ar PMB), 5.94 (d, JZ3.8 Hz, 1H, H1 ),
0
(m, 1H, H2 ), 4.57 (bs, 1H, H4 ), 4.04–3.98 (m, 2H,
0
5.76 (d, JZ8.1 Hz, 1H, H5), 5.02 (dd, JZ5.9, 2.7 Hz, 1H,
0
0
CH2CH2N indoline), 3.88 (d, JZ8.1 Hz, 1H, H5 ), 3.72 (s,
H3 ), 4.99 (d, JZ4.3 Hz, 2H, CH2Ar), 4.83 (dd, JZ5.9,
0
0
3.8 Hz, 1H, H2 ), 4.60 (bs, 1H, OH), 4.53 (bs, 1H, H4 ), 4.35
0
3H, CH3O), 3.61 (d, JZ8.1 Hz, 1H, H6 ), 3.32–3.18 (m, 2H,
0
CH2NHCO), 3.01–2.96 (m, 2H, CH2CH2N indoline), 2.72–
2.66 and 2.47–2.41 (2m, 2H, CH2NH), 1.60–1.58 (m, 2H,
CH2), 1.55 and 1.31 (2s, 6H, C(CH3)2); 13C NMR
(100 MHz, CDCl3) d 172.4, 162.2, 159.0, 156.4, 151.0,
142.3, 139.8, 136.6, 131.9, 131.7, 130.8, 128.5, 128.4,
128.0, 127.3, 124.7, 124.4, 117.3, 114.3, 113.6, 102.4, 94.3,
85.1, 83.1, 81.1, 72.9, 66.4, 61.7, 55.1, 48.1, 45.3, 43.6,
39.1, 29.4, 27.7, 27.2, 25.3; FAB HRMS (NBA): m/e
792.3220, MCNaC calcd for C41H47N5O10 792.3220.
(d, JZ9.1 Hz, 1H, H5 ), 4.12–4.06 and 4.02–3.95 (2m, 2H,
0
CH2CH2N indoline), 3.89 (d, JZ9.1 Hz, 1H, H6 ), 3.72 (s,
3H, CH3O), 3.19–3.00 (m, 2H, CH2CH2N indoline), 1.60
and 1.35 (2s, 6H, C(CH3)2); 13C NMR (100 MHz, CDCl3) d
166.3, 162.2, 159.1, 151.2, 141.9, 139.5, 131.7, 130.9,
128.6, 127.5, 125.0, 124.8, 117.6, 114.7, 113.6, 102.8, 94.4,
84.1, 83.2, 80.9, 71.4, 60.4, 55.2, 48.1, 43.7, 27.8, 27.3,
25.3; FAB HRMS (NBA): m/e 604.2297, MC calcd for
C30H32N6O8 604.2281.
4.2.4. Amino alcohols 15d–j. General procedure. A
solution 0.04–0.07 M of epoxy amide 13 (1.0 equiv) in
MeOH was treated with the corresponding diamine (1.7–
3.0 equiv) with the exception of alcohol 15j, in which the
solvent used was CH3CN. After stirring for 12–30 h at
reflux, the reaction mixture was diluted with toluene and the
solvent was concentrated under reduced pressure for
obtaining 15d, 15e, 15h, 15i, 15j and a mixture 1:1 of 15f
and 15f0. Particularly complete formation of alcohol 15g
required 8 days.
4.2.2. N-Allylamino alcohol 15b. To a solution of epoxy
amide 13 (0.2 g, 0.356 mmol, 1.0 equiv) in MeOH (5 mL)
was added allylamine (82 mL, 1.06 mmol, 3.0 equiv). After
stirring for 12 h at 608, the solution was allowed to warm to
25 8C, and the reaction mixture was diluted with toluene
(1.5 mL) and concentrated under reduced pressure. Purifi-
cation by flash column chromatography (silica gel, 70%
EtOAc, 5% MeOH in hexanes) furnished amino alcohol 15b
(212 mg, 96%) as a white solid: RfZ0.66 (silica gel, 60%
EtOAc, 5% MeOH in hexanes); [a]2D2 C1.8 (c 0.2, CH2Cl2);
1H NMR (400 MHz, CDCl3) d 8.14 (d, JZ7.5 Hz, 1H, Ar
indoline), 7.53 (d, JZ8.1 Hz, 1H, H6), 7.41 (d, JZ9.1 Hz,
2H, Ar PMB), 7.15–7.11 (m, 2H, Ar indoline), 7.01 (dd, JZ
7.0 Hz, 1H, Ar indoline), 6.79 (d, JZ9.1 Hz, 2H, Ar PMB),
4.2.4.1. Compound [15d]. Purification by flash column
chromatography (silica gel, 60% EtOAc, 5% MeOH in
hexanes) provided amino alcohol 15d (81%) as a yellow oil:
RfZ0.56 (silica gel, 70% EtOAc, 5% MeOH in hexanes);
[a]2D2 C1.8 (c 0.1, CH2Cl2); 1H NMR (400 MHz, CDCl3) d
8.12 (d, JZ8.2 Hz, 1H, Ar indoline), 7.65 (d, JZ8.2 Hz,
1H, H6), 7.43 (d, JZ8.8 Hz, 2H, Ar PMB), 7.16–6.99 (m,
3H, Ar indoline), 6.79 (d, JZ8.8 Hz, 2H, Ar PMB), 6.04 (d,
0
5.87 (d, JZ3.8 Hz, 1H, H1 ), 5.82–5.75 (m, 1H, CH2CH),
5.72 (d, JZ8.1 Hz, 1H, H5), 5.15–4.96 (m, 4H, CH2Ar,
0
CH2CH), 4.92 (dd, JZ6.4, 3.2 Hz, 1H, H3 ), 4.79 (dd, JZ
0
0
6.4, 3.8 Hz, 1H, H2 ), 4.60 (d, JZ1.6 Hz, 1H, H4 ), 4.02–
3.97 (m, 2H, CH2CH2N indoline), 3.90 (dd, JZ8.1, 1.6 Hz,
0
0
0
1H, H5 ), 3.73 (s, 3H, CH3O), 3.62 (d, JZ8.1 Hz, 1H, H6 ),
3.25 (dd, JZ14.0, 5.9 Hz, 1H, CH2NH), 3.11 (dd, JZ14.0,
6.4 Hz, 1H, CH2NH), 3.07–2.90 (m, 2H, CH2CH2N indo-
line), 1.57 and 1.33 (2s, 6H, C(CH3)2); 13C NMR (100 MHz,
CDCl3) d 172.8, 162.3, 159.1, 151.0, 142.2, 139.5, 136.6,
JZ4.1 Hz, 1H, H1 ), 5.71 (d, JZ8.2 Hz, 1H, H5), 5.05–4.90
0
0
(m, 3H, H3 , CH2Ar), 4.69 (dd, JZ5.3, 4.1 Hz, 1H, H2 ),
0
4.38 (bs, 1H, H4 ), 4.27 (m, 1H, NHCH3), 4.14–4.06 (m, 1H,
0
CH2CH2N indoline), 3.95–3.88 (m, 2H, H5 , CH2CH2N
indoline), 3.77–3.75 (m, 1H, CH2), 3.74 (s, 3H, CH3O), 3.52

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F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11856
0
(d, JZ8.2 Hz, 1H, H6 ), 3.07–2.99 (m, 3H, CH2CH2N
indoline, CH2), 2.65–2.52 (m, 2H, CH2), 2.40 (s, 3H,
NCH3), 2.35–2.30 (m, 1H, CH2), 1.57 (s, 3H, NHCH3), 1.59
and 1.34 (2s, 6H, C(CH3)2) 1.30–1.25 (m, 1H, CH2); 13C
NMR (100 MHz, CDCl3) d 170.4, 162.4, 159.1, 151.2,
142.5, 139.1, 131.6, 131.0, 128.9, 127.4, 124.7, 124.4,
117.4, 114.2, 113.6, 102.6, 92.6, 84.9, 83.6, 81.5, 69.9, 66.3,
55.2, 51.5, 48.2, 43.7, 39.1, 33.9, 30.9, 29.7, 28.0, 27.5,
25.4; FAB HRMS (NBA): m/e 686.3175, MCNaC calcd for
C35H45N5O8 686.3166.
1H, H5), 5.04 and 4.93 (2d, JZ14.1 Hz, 2H, CH2Ar), 4.89
(dd, JZ5.9, 1.8 Hz, 1H, H3 ), 4.66 (dd, JZ5.9, 4.1 Hz,
0
0
0
0
1H, H2 ), 4.42 (bs, 1H, H4 ), 4.25 (d, JZ8.2 Hz, 1H, H5 ),
4.12–4.02 and 3.94–3.88 (2m, 2H, CH2CH2N indoline),
3.73 (s, 3H, CH3O), 3.76–3.71 (m, 1H, CH2), 3.63 (d, JZ
0
8.2 Hz, 1H, H6 ), 3.46–3.37 (m, 1H, CH2), 3.12–2.92 (m,
2H, CH2CH2N indoline), 2.79–2.61 (m, 4H, CH2CH3),
1.92–1.64 (m, 2H, CH2), 1.59 and 1.34 (2s, 6H, C(CH3)2),
1.55–1.46 and 1.14–1.03 (2m, 2H, CH2), 1.31–1.23 (m, 3H,
CH2CH3), 0.96 (t, JZ7.0 Hz, 3H, CH2CH3); 13C NMR
(100 MHz, CDCl3) d 171.0, 162.5, 159.1, 151.2, 142.6,
138.8, 131.7, 131.0, 128.9, 127.4, 124.7, 124.3, 114.7,
114.1, 113.6, 102.6, 91.9, 84.7, 84.0, 81.6, 70.1, 64.3, 55.2,
49.2, 48.8, 48.2, 46.8, 43.7, 33.9, 28.5, 28.0, 27.5, 25.6,
25.4, 24.9; FAB HRMS (NBA): m/e 714.3485, MCNaC
calcd for C37H49N5O8 714.3479.
4.2.4.2. Compound [15e]. Purification by flash column
chromatography (silica gel, 60% EtOAc, 5% MeOH in
hexanes) provided alcohol 15e (79%) as a white solid: RfZ
0.56 (silica gel, 60% EtOAc, 5% MeOH in hexanes); [a]D22
1
K7.6 (c 0.2, CH2Cl2); H NMR (400 MHz, CDCl3) d 8.13
(d, JZ7.6 Hz, 1H, Ar indoline), 7.63 (d, JZ8.2 Hz, 1H,
H6), 7.43 (d, JZ8.8 Hz, 2H, Ar PMB), 7.16–6.94 (m, 3H,
Ar indoline), 6.77 (d, JZ8.8 Hz, 2H, Ar PMB), 5.97 (d, JZ
4.1 Hz, 1H, H1 ), 5.73 (d, JZ8.2 Hz, 1H, H5), 5.03 and 4.93
(2d, JZ13.5 Hz, 2H, CH2Ar), 4.90 (dd, JZ5.9, 2.3 Hz, 1H,
4.2.4.5. Compound [15h]. Purification by flash column
chromatography (silica gel, 15% MeOH in CH2Cl2) provided
alcohol 15h (165 mg, 73%) as major product and epoxy
amide opening product with NH3 (45 mg, 22%) as minor
product: [15h] white solid: RfZ0.71 (silica gel, 15% MeOH
in CH2Cl2); [a]2D2 K9.4 (c 0.1, CH2Cl2); 1H NMR (400 MHz,
CDCl3) d 8.17 (d, JZ8.1 Hz, 1H, Ar indoline), 7.74 (d, JZ
8.1 Hz, 1H, H6), 7.42 (d, JZ8.6 Hz, 2H, Ar PMB), 7.14–7.11
(m, 2H, Ar indoline), 6.99 (dd, JZ7.5, 7.5 Hz, 1H, Ar
indoline), 6.78 (d, JZ8.6 Hz, 2H, Ar PMB), 5.98 (d, JZ
0
0
0
0
H3 ), 4.68 (dd, JZ5.9, 4.7 Hz, 1H, H2 ), 4.42 (bs, 1H, H4 ),
4.34 (m, 1H, NHCH3), 4.24–4.17 and 3.92–3.85 (2m, 2H,
0
CH2CH2N indoline), 3.76–3.70 (m, 3H, CH2, H5 ), 3.73 (s,
0
3H, CH3O), 3.51 (d, JZ8.8 Hz, 1H, H6 ), 2.97–2.82 (m, 3H,
CH2CH2N indoline, CH2), 2.70–2.65 (m, 1H, CH2), 2.40 (s,
3H, NCH3), 1.56 (s, 3H, NHCH3), 1.55 and 1.33 (2s, 6H,
C(CH3)2); 13C NMR (100 MHz, CDCl3) d 170.2, 162.4,
159.1, 151.3, 142.5, 139.1, 131.5, 131.0, 128.9, 127.4,
124.7, 124.4, 117.2, 114.2, 113.6, 102.7, 92.6, 84.7, 83.6,
81.5, 69.6, 66.7, 55.2, 52.9, 47.9, 43.7, 38.6, 29.7, 27.7,
27.4, 27.3, 25.4; FAB HRMS (NBA): m/e 672.3005, MC
NaC calcd for C34H43N5O8 672.3009.
0
3.8 Hz, 1H, H1 ), 5.74 (d, JZ8.1 Hz, 1H, H5), 4.98 (2d, JZ
0
13.4 Hz, 2H, CH2Ar), 4.89–4.86 (m, 1H, H3 ), 4.74–4.70 (m,
0
1H, H2 ), 4.58 (bs, 1H, H4 ), 4.12–4.01 (m, 2H, CH2CH2N
0
0
indoline), 3.83 (d, JZ7.0 Hz, 1H, H5 ), 3.73 (s, 3H, CH3O),
0
3.65 (d, JZ7.0 Hz, 1H, H6 ), 3.07–2.99 (m, 2H, CH2CH2N
indoline), 2.74–2.42 (m, 4H, CH2), 1.56 and 1.31 (2s, 6H,
C(CH3)2), 1.54–1.49 (m, 2H, CH2); 13C NMR (100 MHz,
CDCl3) d 172.5, 162.5, 159.1, 151.1, 142.3, 139.6, 131.7,
130.1, 128.7, 127.4, 124.8, 124.6, 117.3, 114.3, 113.6, 102.4,
93.4, 85.0, 83.3, 81.5, 72.6, 61.8, 55.2, 48.2, 45.9, 43.7, 40.2,
31.5, 27.8, 27.3, 25.3; FAB HRMS (NBA): m/e 658.2854,
MCNaC calcd for C33H41N5O8 658.2853.
4.2.4.3. Compounds [15f]C[15f0]. Purification by flash
column chromatography (silica gel, 60% EtOAc, 5% MeOH
in hexanes) provided an inseparable 1:1 mixture of alcohols
15f and 15f0 (75%) as a colourless oil: RfZ0.36 (silica gel,
1
60% EtOAc, 5% MeOH in hexanes); H NMR (400 MHz,
CDCl3) d 8.15 and 8.14 (2d, JZ7.0 Hz, 2H, Ar indoline), 7.68
(d, JZ8.2 Hz, 2H, H6), 7.42 and 7.39 (2d, JZ8.2 Hz, 4H, Ar
PMB), 7.19–7.12 (m, 4H, Ar indoline), 7.05–6.97 (m, 2H, Ar
indoline), 6.77(d, JZ8.2 Hz, 4H, ArPMB), 6.08and 5.78(2d,
4.2.4.6. Compound [15i]. Purification by flash column
chromatography (silica gel, 80% EtOAc, 10% MeOH in
hexanes) provided alcohol 15i (62%) as a colourless oil:
RfZ0.64 (silica gel, 80% EtOAc, 10% MeOH in hexanes);
[a]2D2 C5.7 (c 0.04, CH2Cl2); 1H NMR (400 MHz, CDCl3) d
8.16 (d, JZ8.2 Hz, 1H, Ar indoline), 7.49 (d, JZ8.2 Hz,
1H, H6), 7.39 (d, JZ8.8 Hz, 2H, Ar PMB), 7.15–7.12 (m,
2H, Ar indoline), 7.00 (dd, JZ7.0, 7.0 Hz, 1H, Ar indoline),
6.78 (d, JZ8.2 Hz, 2H, Ar PMB), 5.83 (d, JZ2.9 Hz, 1H,
H1 ), 5.74 (d, JZ8.2 Hz, 1H, H5), 4.92–4.50 (m, 3H, H3 ,
0
CH2Ar), 4.82–4.79 (m, 1H, H2 ), 4.54 (bs, 1H, H4), 4.07–
0
3.97 (m, 3H, H5 , CH2CH2N indoline), 3.74–3.72 (m, 1H,
0
H6 ), 3.73 (s, 3H, CH3O), 3.07–3.03 (m, 2H, CH2CH2N
0
JZ4.1 Hz, 2H, H1 ), 5.73 and 5.71 (2d, JZ8.2 Hz, 2H, H5),
0
5.06and4.87(m, 6H, H3 , CH2Ar), 4.80and4.68(2dd, JZ6.4,
0
4.1 Hz, 2H, H2 ), 4.47 and 4.37 (2br s, 2H, H4 ), 4.34–3.84 (m,
0
0
6H, H5 , CH2CH2N indoline), 3.74 and 3.73 (2s, 6H, CH3O),
0
3.53 and 3.47 (2d, JZ8.2 Hz, 2H, H6 ), 3.02–2.97 (m, 4H,
CH2CH2N indoline), 3.10–3.04, 2.69–2.66, 2.60–2.54 and
2.35–2.26 (4m, 8H, CH2), 2.42 (s, 3H, NCH3), 1.75–1.60 (m,
4H, CH2), 1.59, 1.54, 1.34, and 1.31(4s, 2H, C(CH3)2), 1.23(s,
3H, NHCH3); FAB HRMS (NBA): m/e 672.3015, MCNaC
calcd for C34H43N5O8 672.3009.
0
0
indoline), 2.64–2.37 (m, 4H, CH2), 1.59–1.46 (m, 4H, CH2),
1.55 and 1.31 (2s, 6H, C(CH3)2); 13C NMR (100 MHz,
CDCl3) d 162.3, 159.1, 151.1, 142.3, 139.8, 131.6, 130.8,
128.6, 127.4, 124.7, 124.5, 117.4, 114.4, 113.7, 102.5, 94.4,
85.0, 82.9, 81.4, 72.7, 61.8, 55.2, 48.2, 47.5, 43.7, 33.9,
29.7, 27.9, 27.7, 27.3, 25.3; FAB HRMS (NBA): m/e
672.3015, MCNaC calcd for C34H43N5O8 672.3009.
4.2.4.4. Compounds [15g]. Purification by flash column
chromatography (silica gel, 80% EtOAc in hexanes)
provided alcohol 15g (66%) as a white solid: RfZ0.65
(silica gel, 80% EtOAc in hexanes); [a]2D2 C11.6 (c 0.2,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.07 (d, JZ8.2 Hz,
1H, Ar indoline), 7.76 (d, JZ8.2 Hz, 1H, H6), 7.42 (d, JZ
8.8 Hz, 2H, Ar PMB), 7.16–7.10 (m, 2H, Ar indoline), 7.00
(dd, JZ7.6, 7.6 Hz, 1H, Ar indoline), 6.77 (d, JZ8.8 Hz, 2H,
4.2.4.7. Compound [15j]. Purification by flash column
chromatography (silica gel, 10% MeOH in CH2Cl2)
0
Ar PMB), 6.11 (d, JZ4.1 Hz, 1H, H1 ), 5.71 (d, JZ8.2 Hz,

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F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11857
0
provided alcohol 15j (69%) as a colourless oil: RfZ0.43
(silica gel, 10% MeOH in CH2Cl2); [a]2D2 K6.7 (c 0.1,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.17 (d, JZ8.2 Hz,
1H, Ar indoline), 7.77 and 7.72 (2d, JZ8.2 Hz, 1H, H6),
7.41 (d, JZ7.0 Hz, 2H, Ar PMB), 7.14–7.10 (m, 2H, Ar
indoline), 7.01–6.96 (m, 1H, Ar indoline), 6.78 (d, JZ
8.8 Hz, 2H, Ar PMB), 5.97 and 6.00 (2d, JZ3.5 Hz, 1H,
indoline, CHCH2CH(CH3)2), 3.91 (d, JZ7.0 Hz, 1H, H5 ),
0
3.73 (s, 3H, CH3O), 3.59 (d, JZ7.0 Hz, 1H, H6 ), 3.40–3.32
and 3.26–3.17 (2m, 2H, CH2NHCO), 3.08–2.98 (m, 2H,
CH2CH2N indoline), 2.67–2.57 and 2.46–2.40 (2m, 2H,
CH2NH), 1.63–1.50 (m, 5H, CH2, CHCH2CH(CH3)2,
CHCH2CH(CH3)2), 1.56 and 1.31 (2s, 6H, C(CH3)2), 0.87
and 0.85 (2s, 6H, CH(CH3)2); 13C NMR (100 MHz, CDCl3)
d 172.4, 162.3, 159.1, 156.3, 151.1, 142.2, 139.9, 136.2,
131.6, 130.8, 128.6, 128.5, 128.2, 128.0, 127.5, 126.9,
124.7, 124.6, 117.4, 114.4, 113.6, 102.3, 94.6, 84.7, 82.7,
81.4, 72.6, 66.9, 62.0, 55.2, 53.7, 48.2, 45.0, 43.7, 41.1,
37.0, 28.9, 27.9, 27.3, 25.3, 24.7, 22.8, 22.0; FAB HRMS
(NBA): m/e 905.4064, MCNaC calcd for C47H58N6O11
905.4061.
0
0
H1 ), 5.71 (d, JZ8.2 Hz, 1H, H5), 5.03–4.82 (m, 3H, H3 ,
0
0
CH2Ar), 4.74–4.70 (m, 1H, H2 ), 4.60–4.58 (m, 1H, H4 ),
4.15–3.96 (m, 2H, CH2CH2N indoline), 3.78–3.64 (m, 4H,
0
0
H5 , H6 , CH2), 3.71 (s, 3H, CH3O), 3.09–2.99 (m, 2H,
CH2CH2N indoline), 2.65–2.46 (m, 3H, CH, CH2), 1.56 and
1.30 (2s, 6H, C(CH3)2); 13C NMR (100 MHz, CDCl3) d
173.0, 162.4, 159.0, 150.1, 142.2, 139.4, 131.8, 130.8,
128.5, 127.3, 124.8, 124.4, 117.1, 114.1, 113.6, 102.2, 92.7,
85.3, 83.7, 81.5, 72.8, 71.1, 62.3, 55.1, 51.2, 48.0, 45.1,
43.6, 33.8, 27.3, 25.3; FAB HRMS (NBA): m/e 674.2810,
MCNaC calcd for C33H41N5O9 674.2802.
4.5. Amino alcohol 19. Hydrogenation of compound 18
To a solution of compound 18 (0.12 g, 0.136 mmol,
1.0 equiv) in MeOH (4 mL) was added 10% Pd–C
(120 mg). The reaction was allowed to proceed under an
atmosphere of H2 at 25 8C for 30 min. After this time, the
mixture was filtered and the filtrate was washed with MeOH
(2!5 mL). The combined organic solvents were removed
by concentration under reduced pressure and the resulting
residue was subjected to purification by flash column
chromatography (silica gel, 15% MeOH in CH2Cl2) to
afford amino alcohol 19 (71 mg, 70%) as a colourless oil:
RfZ0.56 (silica gel, 10% MeOH in CH2Cl2); [a]2D2 C4.0 (c
4.3. Amino alcohol 15hReduction of N-Z-amino alcohol
15c
A solution of amino alcohol 15c (116 mg, 0.15 mmol,
1.0 equiv) in MeOH (2.0 mL) was treated with 10% Pd–C
(11 mg) and ammonium formate (52 mg, 0.82 mmol,
5.5. equiv) under an Ar atmosphere. The reaction mixture
was refluxed for 2 h and, then, allowed to reach ambient
temperature. The resulting suspension was filtered through a
Celite pad, washed with MeOH (2!5 mL), and the organic
clear solution was concentrated under reduced pressure.
Purification by flash column chromatography (silica gel,
15% MeOH in CH2Cl2) provided amino alcohol 15h
(62 mg, 65%).
1
0.1, CH2Cl2); H NMR (400 MHz, CDCl3) d 8.15 (d, JZ
7.6 Hz, 1H, Ar indoline), 7.72 (d, JZ8.1 Hz, 1H, H6), 7.40
(d, JZ9.1 Hz, 2H, Ar PMB), 7.14–7.10 (m, 2H, Ar
indoline), 7.00 (dd, JZ7.5, 7.5 Hz, 1H, Ar indoline), 6.78
0
(d, JZ9.1 Hz, 2H, Ar PMB), 5.95 (d, JZ3.8 Hz, 1H, H1 ),
0
5.72 (d, JZ8.1 Hz, 1H, H5), 5.01–4.92 (m, 3H, H3 , CH2Ar),
4.75 (dd, JZ4.3, 3.8 Hz, 1H, H2 ), 4.61 (bs, 1H, H4 ), 4.09–
4.05 (m, 2H, CH2CH2N indoline), 3.94 (d, JZ7.5 Hz, 1H,
0
0
4.4. Compound 18. Coupling between Cbz-Leu-OH and
amino alcohol 15h
0
0
H5 ), 3.73 (s, 3H, CH3O), 3.74–3.71 (m, 1H, H6 ), 3.55–3.48
(m, 1H, CHCH2CH(CH3)2), 3.39–3.34 and 3.24–3.16 (2m,
2H, CH2NHCO), 3.11–3.02 (m, 2H, CH2CH2N indoline),
2.72–2.67 and 2.55–2.49 (2m, 2H, CH2NH), 1.67–1.60 (m,
5H, CH2, CHCH2CH(CH3)2, CHCH2CH(CH3)2), 1.54 and
Cbz-Leu-OH (0.3 g, 1.13 mmol, 1.2 equiv) was dissolved in
dry CH2Cl2 (4 mL) and treated with HOBt (0.16 g,
1.13 mmol, 1.2 equiv) at room temperature. After stirring
for 5 min, EDCI (0.22 g, 1.13 mmol, 1.2 equiv) was added
to the reaction mixture, which was stirred for 45 min, prior
to the addition to a solution of 15h (0.59 g, 0.94 mmol,
1.0 equiv) in CH2Cl2 (3 mL). The mixed system was stirred
for an additional 1 h 15 min, after which, aqueous 15% NH3
solution (0.2 mL) was added and the resulting mixture was
diluted with Et2O (5 mL) and washed with a saturated
aqueous NH4Cl soluton (5 mL). The layers were separated
and the aqueous phase was extracted with Et2O (2!5 mL).
The combined organic solution was dried (MgSO4), filtered
and concentrated. Purification by flash column chromatog-
raphy (silica gel, 10% MeOH in CH2Cl2) afforded peptidic
derivative 18 (764 mg, 92%) as a white solid: RfZ0.41
(silica gel, 10% MeOH in CH2Cl2); [a]2D2 K1.6 (c 0.9,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.17 (d, JZ8.1 Hz,
1H, Ar indoline), 7.50 (d, JZ8.1 Hz, 1H, H6), 7.39 (d, JZ
8.6 Hz, 2H, Ar PMB), 7.32–7.27 (m, 5H, aromatics Cbz),
7.14–7.10 (m, 2H, Ar indoline), 7.00 (dd, JZ7.5, 7.5 Hz,
1H, Ar indoline), 6.78 (d, JZ8.6 Hz, 2H, Ar PMB), 5.85 (d,
1.29 (2s, 6H, C(CH3)2), 0.90–0.86 (m, 6H, CH(CH3)2); 13
C
NMR (100 MHz, CDCl3) d 162.4, 159.1, 151.1, 142.2,
139.6, 131.8, 130.8, 128.7, 127.3, 124.8, 124.5, 117.3,
114.2, 113.6, 102.4, 93.2, 84.8, 83.2, 81.6, 72.4, 62.0, 55.2,
53.2, 48.2, 45.6, 43.7, 43.0, 37.1, 29.3, 27.8, 27.3, 25.3,
24.7, 23.1, 21.6; FAB HRMS (NBA): m/e 771.3680, MC
NaC calcd for C39H52N6O9 771.3693.
4.6. Triol 20
Compound 19 (50 mg, 0.057 mmol, 1.0 equiv) was treated
with a solution of TFA/H2O 9:1 (1.7 mL) at 0 8C until the
reaction was complete as judged by TLC (ca. 1.5 h). The
crude mixture was then diluted with toluene and concen-
trated under reduced pressure. Purification by flash column
chromatography (silica gel, 10% MeOH in CH2Cl2)
provided triol 20 (36 mg, 75%) as a white solid: RfZ0.40
(silica gel, 10% MeOH in CH2Cl2); [a]2D2 C7.6 (c 0.3,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.13 (d, JZ8.1 Hz,
1H, H6), 7.73 (d, JZ7.5 Hz, 1H, Ar indoline), 7.37 (d, JZ
8.6 Hz, 2H, Ar PMB), 7.26–7.22 (m, 5H, aromatics Cbz),
7.13–7.06 (m, 2H, Ar indoline), 6.98 (dd, JZ7.5, 7.5 Hz,
0
JZ3.2 Hz, 1H, H1 ), 5.71 (d, JZ8.1 Hz, 1H, H5), 5.46 (bs,
1H, NHCbz), 5.09–4.95 (m, 4H, CH2ArPMB, CH2ArCbz),
0
4.91 (dd, JZ6.4, 2.7 Hz, 1H, H3 ), 4.82 (d, JZ6.4, 3.2 Hz,
0
1H, H2 ), 4.56 (bs, 1H, H4 ), 4.10–4.00 (m, 3H, CH2CH2N
0

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F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11858
0
1H, Ar indoline), 6.75 (d, JZ8.6 Hz, 2H, Ar PMB), 5.89
(bs, 1H, H1 ), 5.74 (bs, 1H, NHCbz), 5.70 (d, JZ8.1 Hz, 1H,
H5), 5.05–4.90 (m, 4H, CH2ArPMB, CH2ArCbz), 4.41 (bs,
3.50 (d, JZ2.1 Hz, 1H, H6 ), 1.54 and 1.33 (2s, 6H,
C(CH3)2); 13C NMR (100 MHz, CDCl3) d 168.4, 162.2,
159.1, 139.0, 130.7, 114.8, 113.7, 102.9, 94.0, 84.8, 84.3,
81.6, 57.4, 55.2, 52.7, 50.2, 43.6, 27.1, 25.3; FAB HRMS
(NBA): m/e 497.1532, MCNaC calcd for C23H26N2O9
497.1536.
0
0
1H, H4 ), 4.29–3.94 (m, 6H, H2 , H3 , H5 , CH2CH2N
0
0
0
0
indoline, CHCH2CH(CH3)2), 3.73–3.70 (m, 1H, H6 ), 3.72
(s, 3H, CH3O), 3.35–3.28 and 3.19–3.13 (2m, 2H, CH2-
NHCO), 3.05–3.01 (m, 2H, CH2CH2N indoline), 2.66–2.58
and 2.47–2.41 (2m, 2H, CH2NH), 1.62–1.45 (m, 5H, CH2,
CHCH2CH(CH3)2, CHCH2CH(CH3)2), 0.89–0.82 (m, 6H,
CH(CH3)2); 13C NMR (100 MHz, CDCl3) d 172.9, 162.5,
159.0, 156.5, 151.3, 142.1, 138.8, 136.0, 132.0, 130.7,
128.8, 128.5, 128.2, 127.8, 127.4, 124.9, 124.7, 117.3,
113.6, 102.0, 91.2, 84.2, 74.7, 72.2, 70.7, 67.0, 62.0, 55.2,
53.7, 48.2, 44.9, 43.6, 41.0, 37.1, 30.0, 27.8, 24.6, 22.8,
21.9; FAB HRMS (NBA): m/e 865.3752, MCNaC calcd for
C44H54N6O11 865.3748.
4.9. Isopropyl epoxy ester 24
To a stirred solution of methyl epoxy ester 23 (45 mg,
0.095 mmol, 1.0 equiv) in 2-methyl-2-propanol (2.5 mL)
was added Bu2SnO (2.4 mg, 9.5 mmol, 0.1 equiv). The
reaction mixture was then heated at reflux with complete
depletion of starting material after 12 h, according to TLC
analysis. The crude mixture was allowed to warm to 25 8C,
diluted with EtOAc (5 mL) and washed with saturated
aqueous NaHCO3 solution (5 mL). The aqueous solution
was extracted with EtOAc (2!5 mL) and the combined
organic layers were dried over MgSO4, filtered through a
pad of Celite and concentrated under reduced pressure.
Purification by flash column chromatography (silica gel,
40% EtOAc, 5% MeOH in hexanes) furnished epoxy ester
24 (32 mg, 67%) as a white solid: RfZ0.57 (silica gel, 40%
EtOAc, 5% MeOH in hexanes); [a]2D2 C8.0 (c 0.1, CH2Cl2);
1H NMR (400 MHz, CDCl3) d 7.40 (d, JZ8.6 Hz, 2H, Ar),
7.23 (d, JZ8.1 Hz, 1H, H6), 6.80 (d, JZ8.6 Hz, 2H, Ar),
4.7. N,N-Dimethyl epoxy amide 22
A solution of epoxy-indole amide 2118 (89 mg, 0.159 mmol,
1.0 equiv) in THF (2 mL) was treated with dimethylamine
(26 mL, 0.207 mmol, 1.3 equiv) and the mixture was stirred
at room temperature for 5 h. After this time, the crude
mixture was concentrated under reduced pressure. Purifi-
cation by flash column chromatography (silica gel, 70%
EtOAc, 5% MeOH in hexanes) provided epoxy amide 22
(51 mg, 66%) as major product together with the N,N-
dimethyl amino alcohol opening product (16 mg, 19%) as
minor product.
0
5.88 (d, JZ2.7 Hz, 1H, H1 ), 5.77 (d, JZ8.1 Hz, 1H, H5),
5.12–4.93 (m, 4H, H3 , CH2Ar, CH(CH3)2), 7.81 (dd, JZ
6.4, 2.7 Hz, 1H, H2 ), 4.19 (dd, JZ3.8, 3.8 Hz, 1H, H4 ),
3.75 (s, 3H, CH3O), 3.53 (dd, JZ3.8, 1.6 Hz, 1H, H5 ), 3.45
0
0
0
0
0
Compound [22]. White solid; RfZ0.40 (silica gel, 100%
EtOAc); [a]2D2 C18.9 (c 1.0, CH2Cl2); 1H NMR (400 MHz,
CDCl3) d 7.42 (d, JZ8.6 Hz, 2H, Ar), 7.30 (d, JZ8.1 Hz,
1H, H6), 6.79 (d, JZ8.6 Hz, 2H, Ar), 5.98 (d, JZ2.7 Hz,
(d, JZ1.6 Hz, 1H, H6 ), 1.55 and 1.33 (2s, 6H, C(CH3)2),
1.27 and 1.26 (2s, 6H, CH(CH3)2); 13C NMR (100 MHz,
CDCl3) d 167.4, 162.2, 159.1, 150.8, 138.7, 130.7, 128.7,
114.8, 113.7, 102.9, 93.2, 84.2, 84.0, 81.5, 70.0, 57.3, 55.2,
50.5, 43.6, 27.1, 25.3, 21.7, 21.6; FAB HRMS (NBA): m/
eZ525.1852, MCNaC calcd for C25H30N2O9 525.1849.
0
1H, H1 ), 5.76 (d, JZ8.1 Hz, 1H, H5), 5.04 and 4.95 (2d, JZ
0
14.0 Hz, 2H, CH2Ar), 4.93 (dd, JZ5.9, 3.8 Hz, 1H, H3 ),
0
4.75 (dd, JZ5.9, 2.7 Hz, 1H, H2 ), 4.25 (dd, JZ3.8, 3.8 Hz,
0
0
1H, H4 ), 3.75 (s, 3H, CH3O), 3.67 (d, JZ2.1 Hz, 1H, H6 ),
4.10. Amino alcohol 25
0
3.49 (dd, JZ3.8, 2.1 Hz, 1H, H5 ), 3.09 and 2.96 (2s, 6H,
N(CH3)2), 1.56 and 1.33 (2s, 6H, C(CH3)2); 13C NMR
(100 MHz, CDCl3) d 165.9, 162.2, 159.1, 150.8, 138.4,
130.9, 128.7, 114.8, 113.6, 103.0, 92.4, 83.9, 83.2, 81.4,
57.2, 55.2, 50.4, 43.7, 36.4, 35.7, 27.2, 25.3; FAB HRMS
(NBA): m/e 487.1945, MC calcd for C24H29N3O8 487.1955.
A solution of N-Z-1,3-diaminopropane hydrochloride
(34.4 mg, 0.14 mmol, 1.4 equiv) in MeOH (2 mL) was
treated with triethylamine (28 mL, 0.2 mmol, 2.0 equiv) for
30 min at room temperature. After this time, this solution
was added to a solution of epoxy amide 22 (49 mg,
0.1 mmol, 1.0 equiv) in MeOH (2 mL) and the resulting
reaction mixture was heated under reflux for 8 days. Then,
the mixture was allowed to reach room temperature and
toluene (1.0 mL) was added. The resulting azeotropic
solution was concentrated under reduced pressure and the
crude product was purified by flash column chromatography
(silica gel, 75% EtOAc, 5% MeOH in hexanes) to furnish
amino alcohol 25 (41 mg, 33%) as a white solid: RfZ0.26
(silica gel, 75% EtOAc, 5% MeOH in hexanes); [a]D22
C22.9 (c 0.7, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 7.39
(d, JZ8.6 Hz, 2H, Ar PMB), 7.32–7.27 (m, 6H, aromatics
Cbz, H6), 6.77 (d, JZ8.6 Hz, 2H, Ar PMB), 5.74–5.69 (m,
2H, H1 , H5), 5.38 (bs, NHCbz), 5.10–4.98 (m, 4H,
CH2ArPMB, CH2ArCbz) 4.91 (dd, JZ6.4, 3.2 Hz, 1H,
H3 ), 4.81–4.79 (m, 1H, H2 ), 4.47 (bs, 1H, H4 ), 3.80 (d, JZ
8.1 Hz, 1H, H5 ), 3.74 (bs, 4H, CH3O, H6 ), 3.28–3.17 (m,
2H, CH2NHCO), 2.91 (s, 6H, N(CH3)2), 2.64–2.58 and
2.42–2.36 (2m, 2H, CH2NH), 1.60–1.55 (m, 2H, CH2), 1.54
and 1.31 (2s, 6H, C(CH3)2); 13C NMR (100 MHz, CDCl3)
4.8. Methyl epoxy ester 23
To a solution of epoxy-indole amide 21 (78 mg,
0.139 mmol, 1.0 equiv) in MeOH (2.5 mL) was added
triethylamine (20 mL, 0.139 mmol, 1.0 equiv), and the
reaction mixture was stirred for 30 min at 25 8C. After this
time, the solvent was removed by concentration under
reduced pressure and the crude product was purified by flash
column chromatography (silica gel, 40% EtOAc, 5% MeOH
in hexanes) to obtain epoxy ester 23 (66 mg, 99%) as a
white solid: RfZ0.43 (silica gel, 40% EtOAc, 5% MeOH in
hexanes); [a]2D2 C14.0 (c 0.1, CH2Cl2); 1H NMR (400 MHz,
CDCl3) d 7.40 (d, JZ8.6 Hz, 2H, Ar), 7.20 (d, JZ8.1 Hz, 1H,
0
0
0
0
0
H6), 6.80 (d, JZ8.6 Hz, 2H, Ar), 5.82 (d, JZ2.7 Hz, 1H, H1 ),
0
0
5.76 (d, JZ8.1 Hz, 1H, H5), 5.03 and 4.96 (2d, JZ14.0 Hz,
0
2H, CH2Ar), 4.95 (dd, JZ6.4, 4.3 Hz, 1H, H3 ), 4.83 (dd, JZ
0
0
6.4, 2.7 Hz, 1H, H2 ), 4.12 (dd, JZ4.3, 4.3 Hz, 1H, H4 ), 3.78
0
and 3.75 (2s, 6H, CH3O), 3.55 (dd, JZ4.3, 2.1 Hz, 1H, H5 ),

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F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11859
d 173.3, 162.3, 159.0, 156.5, 151.1, 140.0, 130.8, 128.7,
128.5, 128.0, 114.4, 113.6, 102.4, 94.6, 85.1, 83.0, 81.1,
72.4, 66.4, 58.8, 55.2, 45.3, 43.6, 39.1, 37.2, 35.8, 29.3,
27.3, 25.3; FAB HRMS (NBA): m/e 718.3071, MCNaC
calcd for C35H45N5O10 718.3064.
(3 mL) was added and the combined organic solution was
filtered, washed with t-butyl methyl ether and hexanes, and
concentrated under reduced pressure. Thus, the resulting
sulfur ylide was dissolved in CH2Cl2 (3 mL) and treated
with crude aldehyde 29 (w0.352 mmol, 1.0 equiv),
obtained by oxidation of its corresponding alcohol (0.1 g,
0.370 mmol) with DMP, at 0 8C. After 2.5 h, the crude
mixture was concentrated under reduced pressure. Purifi-
cation by flash column chromatography (silica gel, 80%
EtOAc in hexanes) afforded epoxy amide 32 (46 mg, 43%
from precursor alcohol of aldehyde 29) as a white solid:
RfZ0.51 (silica gel, 100% EtOAc); [a]2D2 C24.0 (c 0.1,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 9.70 (bs, 1H, NH),
8.13 (d, JZ8.6 Hz, 1H, Ar), 7.34 (d, JZ8.1 Hz, H6), 7.17–
7.13 (m, 2H, Ar), 7.01 (dd, JZ7.0, 7.0 Hz, 1H, Ar), 5.89 (d,
4.11. Amino alcohol 26
A solution of epoxy amide 22 (61 mg, 0.125 mmol,
1.0 equiv) in MeOH (2 mL) was treated with 1,3-diamino-
propane (21 mL, 0.25 mmol, 2.0 equiv) for 48 h at 70 8C.
After this time, the mixture was allowed to reach room
temperature and toluene (1.0 mL) was added. Then, the
solution was concentrated under reduced pressure and the
crude product was used in the coupling step without
purification.
0
JZ2.1 Hz, 1H, H1 ), 5.71 (dd, JZ8.1, 1.6 Hz, 1H, H5), 4.99
0
(dd, JZ6.4, 3.8 Hz, 1H, H3 ), 4.84 (dd, JZ6.4, 2.1 Hz, 1H,
0
H2 ), 4.24–4.13 (m, 3H, H4 , CH2CH2N indoline), 3.68 (d,
0
4.12. Compound 28
0
0
JZ2.1 Hz, 1H, H6 ), 3.63–3.62 (m, 1H, H5 ), 3.23–3.16 (m,
2H, CH2CH2N indoline), 1.55 and 1.33 (2s, 6H, C(CH3)2);
13C NMR (100 MHz, CDCl3) d 172.5, 163.1, 150.2, 142.3,
141.9, 131.7, 127.2, 124.9, 124.7, 117.4, 114.3, 102.5, 92.1,
84.7, 83.2, 81.9, 57.8, 50.5, 49.3, 48.7, 44.9, 30.0, 27.9,
27.5, 25.1; FAB HRMS (NBA): m/e 464.1429, MCNaC
calcd for C22H23N3O7 464.1434.
Cbz-Leu-OH (40 mg, 0.15 mmol, 1.2 equiv) was dissolved
in dry CH2Cl2 (2 mL) and treated with HOBt (21 mg,
0.15 mmol, 1.2 equiv) at room temperature. After stirring
for 5 min, EDCI (29.4 mg, 0.15 mmol, 1.2 equiv) was added
to the solution. The mixture was stirred for 45 min and then,
the crude mixture was added to a solution of amino alcohol
26 (w0.125 mmol, 1.0 equiv) in CH2Cl2 (2 mL). The
reaction mixture was then stirred for additional 3 h. After
that time, a 15% aqueous NH3 solution (0.5 mL) was added
and the reaction mixture was diluted with Et2O (10 mL) and
washed with a saturated aqueous NH4Cl solution (10 mL).
The layers were separated and the aqueous phase was
extracted with Et2O (2!5 mL). The combined organic
phase was dried (MgSO4), filtered and concentrated.
Purification by flash column chromatography (silica gel,
10% MeOH in EtOAc) afforded peptidic derivative 28
(36 mg, 36% over two steps from 22) as a white solid: RfZ
0.40 (silica gel, 10% MeOH in EtOAc); [a]2D2 C10.6 (c 0.8,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 7.54 (d, JZ8.1 Hz,
1H, H6), 7.40 (d, JZ8.6 Hz, 2H, Ar PMB), 7.32–7.29 (m,
5H, aromatics Cbz), 6.78 (d, JZ8.6 Hz, 2H, Ar PMB), 5.87
4.14. Epoxy amide 33
To a solution of crude aldehyde 30 (w0.9 g, 1.9 mmol,
1.0 equiv), prepared from its corresponding alcohol (0.93 g,
1.9 mmol) by oxidation with IBX, in CH2Cl2 (8 mL) was
added at 0 8C, sulfonium salt 31 (0.56 g, 2.16 mmol,
1.1 equiv) and a 20% aqueous NaOH solution (0.43 mL,
2.16 mmol, 1.1 equiv). After stirring for 1.5 h, the crude
mixture was diluted with H2O (10 mL), the layers were
separated and the aqueous phase was extracted with EtOAc
(1!10 mL). The combined organic extracts were dried
(MgSO4) and concentrated under reduced pressure. Purifi-
cation by flash column chromatography (silica gel, 50%
EtOAc in hexanes) gave epoxy amide 33 (0.76 g, 61% over
two steps from its corresponding alcohol) as a white solid:
RfZ0.45 (silica gel, 50% EtOAc in hexanes); [a]2D2 C51.3
(c 1.4, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.83 (bs, 1H,
NH), 8.17 (d, JZ8.1 Hz, 1H, H6), 7.75 (d, JZ8.1 Hz, 1H, Ar),
7.22–7.19 (m, 2H, Ar), 7.06 (dd, JZ7.0, 7.0 Hz, 1H, Ar), 5.98
0
(bs, 1H, H1 ), 5.74 (d, JZ8.1 Hz, 1H, H5), 5.63 (bs, 1H,
NHCbz), 5.09–4.96 (m, 4H, CH2ArPMB, CH2ArCbz), 4.89
0
0
(dd, JZ6.4, 2.7 Hz, 1H, H3 ), 4.82–4.79 (m, 1H, H2 ), 4.44
0
(bs, 1H, H4 ), 4.10–4.04 (m, 1H, CHCH2CH(CH3)2), 3.96–
0
0
3.86 (m, 1H, H5 ), 3.78–3.73 (m, 1H, H6 ), 3.75 (s, 3H,
CH3O), 3.40–3.33 and 3.27–3.19 (2m, 2H, CH2NHCO),
2.95–2.91 (m, 6H, N(CH3)2), 2.60–2.52 and 2.48–2.39 (2m,
2H, CH2NH), 1.62–1.51 (m, 5H, CH2, CHCH2CH(CH3)2,
CHCH2CH(CH3)2), 1.56 and 1.31 (2s, 6H, C(CH3)2), 0.92–
0.85 (m, 6H, CH(CH3)2); 13C NMR (100 MHz, CDCl3) d
172.7, 164.4, 159.1, 156.3, 151.1, 140.0, 136.3, 130.9,
130.7, 128.7, 128.5, 128.1, 128.0, 127.9, 114.5, 113.6,
102.6, 94.4, 84.8, 82.7, 81.3, 71.6, 66.9, 59.4, 55.2, 53.6,
44.9, 43.7, 43.6, 41.1, 37.3, 35.9, 29.6, 27.3, 25.3, 24.7,
22.7, 22.0; FAB HRMS (NBA): m/e 808.4001, MCNaC
calcd for C41H56N6O11 808.4007.
0
(d, JZ4.8 Hz, 1H, H1 ), 5.76(dd,JZ8.1,2.1 Hz, 1H, H5),4.35
0
(d, JZ3.2 Hz, 1H, H4 ), 4.20–4.16 (m, 2H, CH2CH2N
0
0
indoline), 4.11–4.09 (m, 2H, H2 , H3 ), 3.78 (d, JZ2.1 Hz,
0
0
1H, H6 ), 3.51 (d, JZ2.1 Hz, 1H, H5 ), 3.28–3.24 (m, 2H,
CH2CH2N indoline), 0.90 and 0.86 (2s, 18H, C(CH3)3), 0.12,
0.11, 0.05, and 0.03(4s, 12H, Si(CH3)2);13C NMR(100 MHz,
CDCl3) d 163.8, 162.8, 150.4, 142.2, 139.5, 130.9, 127.7,
124.7, 124.6, 117.3, 103.0, 87.8, 79.2, 74.8, 73.6, 57.2, 50.6,
47.3, 28.1, 25.7, 25.6, 18.1, 17.9, K4.9, K4.8, K4.6, K4.5;
FAB HRMS (NBA): m/e 652.2846, MCNaC calcd for
C31H47N3O7Si2 652.2850.
4.13. Epoxy amide 32
4.15. Azido alcohol 34
A solution of sulfonium salt 31 (93 mg, 0.361 mmol,
1.03 equiv) in CH3CN (2.5 mL) was treated with NaH
(45 mg, 1.13 mmol, 3.2 equiv). The reaction mixture was
stirred at 25 8C for 3 h. After this time, t-butyl methyl ether
A solution of epoxy amide 32 (46 mg, 0.104 mmol,
1.0 equiv) in MeOH (2 mL) was treated with a 6.4 M
1-azido-3-propanoamine solution in Et2O (16 mL,
0.104 mmol, 1.0 equiv). After stirring at 70 8C for 72 h,

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11860
the crude mixture was diluted with toluene (0.5 mL) and
concentrated in vacuo. Purification by flash column
chromatography (silica gel, 100% EtOAc) provided
compound 34 (27 mg, 48%) as a white solid: RfZ0.44
(c 0.4, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.78 (bs, 1H,
NH), 8.20 (d, JZ8.1 Hz, 1H, Ar indoline), 7.34–7.26 (m,
6H, aromatics Cbz, H6), 7.18–7.14 (m, 2H, Ar indoline),
7.02 (dd, JZ7.5, 7.5 Hz, 1H, Ar indoline), 5.61 (d, JZ
(silica gel, 100% EtOAc); [a]2D2 K7.2 (c 0.5, CH2Cl2); H
8.1 Hz, 1H, H5), 5.51 (d, JZ5.4 Hz, 1H, H1 ), 5.27 (bs, 1H,
1
0
NMR (400 MHz, CDCl3) d 8.20 (d, JZ7.5 Hz, 1H, Ar),
7.64 (d, JZ8.1 Hz, 1H, H6), 7.17–7.13 (m, 2H, Ar), 7.01
(dd, JZ7.0, 7.0 Hz, 1H, Ar), 5.90 (d, JZ3.4 Hz, 1H, H1 ),
NHCbz), 5.04 (2d, JZ12.4 Hz, 2H, CH2Ar), 4.49–4.45 (m,
0
1H, H2 ), 4.33 (br s, 1H, H4 ), 4.17–4.10 (m, 3H, H3 ,
0
0
0
0
0
CH2CH2N indoline), 3.96–3.81 (br s, 2H, H5 , H6 ), 3.32–
3.23 (m, 2H, CH2NHCO), 3.17–3.13 (m, 2H, CH2CH2N
indoline), 2.77 and 2.54 (2bs, 2H, CH2NH), 1.66 (bs, 2H,
CH2), 0.86 and 0.81 (2s, 18H, C(CH3)3), 0.05, 0.04, K0.004
and K0.07 (4s, 12H, Si(CH3)2); 13C NMR (100 MHz,
CDCl3) d 162.8, 156.6, 150.4, 142.7, 142.2, 136.6, 131.6,
128.5, 128.1, 128.0, 127.5, 124.7, 117.5, 102.4, 92.3, 86.1,
73.1, 73.0, 66.7, 62.2, 58.1, 48.2, 45.2, 38.6, 28.0, 25.7,
18.0, 17.9, K4.5, K4.6, K4.7, K5.0; FAB HRMS (NBA):
m/e 860.4066, MCNaC calcd for C42H63N5O9Si2
860.4062.
5.67 (d, JZ8.1 Hz, 1H, H5), 4.91 (dd, JZ5.9, 2.7 Hz, 1H,
0
0
0
H3 ), 4.80 (dd, JZ5.9, 3.4 Hz, 1H, H2 ), 4.59 (bs, 1H, H4 ),
4.16–4.04 (m, 2H, CH2CH2N indoline), 3.88 (d, JZ8.6 Hz,
0
0
1H, H5 ), 3.68 (d, JZ8.6 Hz, H6 ), 3.40–3.27 (m, 2H,
CH2N3), 3.12–3.06 (m, 2H, CH2CH2N indoline), 2.75–2.64
and 2.55–2.49 (2m, 2H, CH2NH), 1.72–1.65 (m, 2H, CH2),
1.57 and 1.33 (2s, 6H, C(CH3)2); 13C NMR (100 MHz,
CDCl3) d 172.7, 163.2, 150.4, 142.1, 141.8, 131.8, 127.5,
124.8, 124.6, 117.4, 114.4, 102.8, 92.8, 84.9, 83.1, 81.4,
73.0, 61.6, 49.2, 48.2, 44.8, 29.4, 27.8, 27.3, 25.3; FAB
HRMS (NBA): m/e 564.2288, MCNaC calcd for
C25H31N7O7 564.2183.
4.18. Amino alcohol 37
4.16. Azido alcohol 35
Procedure A. A solution of azido alcohol 35 (19 mg,
0.028 mmol, 1.0 equiv) in THF (1.0 mL) was treated with
Ph3P (29 mg, 0.11 mmol, 4.0 equiv) at room temperature
for 1 h. After this time, H2O (1 mL) was added and the
resulting mixture was vigorously stirred for additional 5 h.
After this time, the crude mixture was diluted with Et2O, the
phases were separated and the aqueous phase was extracted
with Et2O (2!5 mL). The combined ethereal solution was
washed with brine, dried (MgSO4), filtered and concentrated
to obtain a crude product, which was purified by flash
column chromatography (silica gel, 10/15% MeOH in
CH2Cl2) to provide amino alcohol 37 (15 mg, 75%) as a
white solid. Procedure B. A solution of alcohol 36 (113 mg,
0.135 mmol, 1.0 equiv) in EtOH (10 mL) was treated with
Pd–C 10% wt (0.15 g) and HCOONH4 25% w/v (1.7 mL)
under Ar atmosphere. After stirring for 30 min at room
temperature, the mixture was filtered through a pad of
Celite, and the filtrates were washed with MeOH (2!5 mL)
and concentrated under reduced pressure. The crude mixture
was purified by flash column chromatography (silica gel,
10/15% MeOH in CH2Cl2) to provide amino alcohol 37
(68 mg, 72%): RfZ0.32 (silica gel, 10% MeOH in CH2Cl2);
[a]2D2 K5.1 (c 0.4, CH2Cl2); 1H NMR (400 MHz, CDCl3) d
8.20 (d, JZ8.6 Hz, 1H, Ar), 8.02 (bs, 1H, H6), 7.18–7.14
(m, 2H, Ar), 7.02 (dd, JZ7.5 Hz, 1H, Ar) 6.03 (d, JZ
A solution of epoxy amide 33 (0.2 g, 0.318 mmol,
1.0 equiv) in MeOH (7 mL) was treated with a 6.4 M of
1-azido-3-propanoamine solution in Et2O (0.1 mL,
0.68 mmol, 2.1 equiv). After stirring at 70 8C for 48 h, the
crude mixture was then diluted with toluene (1.0 mL) and
concentrated in vacuo. Purification by flash column
chromatography (silica gel, 50% EtOAc in hexanes)
provided compound 35 (193 mg, 83%) as a white solid:
RfZ0.41 (silica gel, 50% EtOAc in hexanes); [a]2D2 K7.2 (c
1
0.5, CH2Cl2); H NMR (400 MHz, CDCl3) d 9.03 (bs, 1H,
NH), 8.22 (d, JZ8.1 Hz, 1H, H6), 7.68 (d, JZ8.1 Hz, 1H,
Ar), 7.19–7.17 (m, 2H, Ar), 7.03 (dd, JZ7.0, 7.0 Hz, 1H,
Ar), 5.68 (d, JZ8.1 Hz, 1H, H5), 5.62 (d, JZ6.4 Hz, 1H,
0
0
0
H1 ), 4.43 (dd, JZ6.4, 4.8 Hz, 1H, H2 ), 4.39 (bs, 1H, H4 ),
0
4.20–4.09 (m, 3H, H3 , CH2CH2N indoline), 3.80–3.71 (m,
0
0
2H, H5 , H6 ), 3.41–3.28 (m, 2H, CH2N3), 3.16–3.12 (m, 2H,
CH2CH2N indoline), 2.79–2.73 and 2.60–2.51 (2m, 2H,
CH2NH), 1.72–1.67 (m, 2H, CH2), 0.88 and 0.82 (2s, 18H,
C(CH3)3), 0.06, 0.003, and K0.05 (3s, 12H, Si(CH3)2); 13
C
NMR (100 MHz, CDCl3) d 163.1, 150.4, 142.4, 142.2,
131.7, 127.5, 124.7, 124.6, 117.5, 102.3, 91.8, 85.6, 73.5,
73.0, 72.0, 61.8, 49.1, 48.2, 44.8, 27.9, 25.8, 25.7, 18.0,
17.9, 2.2, 1.9, 1.7; FAB HRMS (NBA): m/e 752.3584, MC
NaC calcd for C34H55N7O7Si2 752.3599.
0
7.0 Hz, 1H, H5), 5.65 (d, JZ4.3 Hz, 1H, H1 ), 4.42–4.00 (m,
0
6H, H2 , H3 , H5 , H6 , CH2CH2N indoline) 4.12 (bs, 1H,
0
0
0
0
H4 ), 3.39–3.14 (m, 4H, CH2CH2N indoline, CH2NH), 3.10
4.17. Amino alcohol 36
and 2.66 (2bs, 2H, CH2NH2), 1.99 and 1.72 (2bs, 2H, CH2),
0.80 and 0.70 (2s, 18H, C(CH3)3), K0.003, K0.02, K0.04,
K0.1 (4s, 12H, Si(CH3)2); 13C NMR (100 MHz, CDCl3) d
169.6, 164.8, 153.8, 150.7, 142.5, 131.4, 127.4, 124.5,
124.3, 117.5, 102.7, 91.3, 85.5, 73.5, 68.4, 64.4, 48.2, 47.8,
41.2, 29.6, 28.3, 25.6, 24.3, 17.8, K4.5, K4.7, K4.9; FAB
HRMS (NBA): m/e 726.3687, MCNaC calcd for
C34H57N5O7Si2 726.3694.
A solution of N-Z-1,3-diaminopropane hydrochloride
(0.16 g, 0.63 mmol, 2.0 equiv) in MeOH (2 mL) was treated
with triethylamine (0.13 mL, 0.906 mmol, 2.9 equiv) for
30 min at room temperature. After this time, the resulting
mixture was added to a solution of epoxy amide 33 (0.2 g,
0.318 mmol, 1.0 equiv) in MeOH (4 mL) and the reaction
mixture was stirred under reflux for 48 h. Then, the mixture
was allowed to reach room temperature and toluene
(1.0 mL) was added. The solution was concentrated under
reduced pressure and the crude product was purified by flash
column chromatography (silica gel, 80% EtOAc in hexanes)
to provide amino alcohol 36 (0.22 g, 83%) as a white solid:
RfZ0.56 (silica gel, 80% EtOAc in hexanes); [a]2D2 K4.0
4.19. Peptidic derivative 38
Z-Leu-OH (29.4 mg, 0.11 mmol, 1.3 equiv) was dissolved
in dry CH2Cl2 (1 mL) and treated with HOBt (15.3 mg,
0.11 mmol, 1.3 equiv) at room temperature. After stirring

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F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11861
for 5 min, EDCI (21.7 mg, 0.11 mmol, 1.3 equiv) was added
to the solution and the resulting mixture was stirred for
45 min and added to a solution of 37 (60 mg, 0.085 mmol,
1.0 equiv) in CH2Cl2 (1.5 mL). The reaction mixture was
then stirred for additional 6 h. After that time, a 15%
aqueous NH3 solution (0.2 mL) was added and the crude
mixture was diluted with Et2O (4 mL) and washed with
NH4Cl (4 mL). The layers were separated and the aqueous
phase was extracted with Et2O (2!4 mL). The combined
organic phase was dried over MgSO4, filtered and
concentrated. Purification by flash column chromatography
(silica gel, 5% MeOH in CH2Cl2) afforded peptidic
derivative 38 (60 mg, 74%) as a white solid: RfZ0.58
(silica gel, 10% MeOH in CH2Cl2); [a]2D2 K10.8 (c 1.5,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.21 (d, JZ7.5 Hz,
1H, Ar indoline), 7.50 (bs, 1H, H6), 7.34–7.25 (m, 4H,
aromatics Cbz), 7.17–7.12 (m, 2H, Ar indoline), 7.01 (dd,
JZ7.5, 7.5 Hz, 1H, Ar indoline) 5.65 (d, JZ7.5 Hz, 1H,
K4.6, K4.7, K5.0; FAB HRMS (NBA): m/e 817.4718,
MCNaC calcd for C40H68N6O8Si2 817.4715.
4.21. Epoxy indole amide 40
A solution of epoxy amide 33 (0.47 g, 0.75 mmol,
1.0 equiv) in C6H6 (8 mL) was treated with DDQ (0.89 g,
3.73 mmol, 5.0 equiv) for 24 h at 80 8C. After this time, the
reaction mixture was allowed to reach room temperature
and diluted with CHCl3 (10 mL) and washed sequentially
with a saturated aqueous NaHCO3 solution (3!10 mL) and
brine (5 mL). The combined organic solution was concen-
trated under reduced pressure and the crude product was
purified by flash column chromatography (silica gel, 40%
EtOAc in hexanes) to afford epoxy amide 40 (0.40 g, 86%)
as a white solid: RfZ0.73 (silica gel, 50% EtOAc in
hexanes); [a]2D2 C44.0 (c 0.3, CH2Cl2); 1H NMR (400 MHz,
CDCl3) d 9.33 (bs, 1H, NH), 8.39 (d, JZ6.4 Hz, 1H, Ar),
7.73 (d, JZ8.6 Hz, 1H, H6), 7.58–7.56 and 7.39–7.29 (2m,
4H, CHCHN indoline, Ar), 6.73 (d, JZ3.8 Hz, 1H, CHCHN
0
H5), 5.53 (bs, 1H, H1 ), 5.07 (2d, JZ12.4 Hz, 2H, CH2Ar),
0
4.57 (bs, 1H, H2 ) 4.30 (bs, 1H, H4 ), 4.27–4.07 (m, 4H,
0
0
CH2CH2N indoline, H3 , CHCH2CH(CH3)2), 3.83 (bs, 1H,
0
indoline), 5.98 (d, JZ4.8 Hz, 1H, H1 ), 5.79 (dd, JZ8.6,
0
0
0
H5 ), 3.70 (bs, 1H, H6 ), 3.36–3.24 (m, 2H, CH2NHCO),
3.17–3.11 (m, 2H, CH2CH2N indoline), 2.78–2.70 and
2.57–2.51 (2m, 2H, CH2NH), 1.67–1.41 (m, 5H, CH2,
CHCH2CH(CH3)2, CHCH2CH(CH3)2), 0.87–0.82 (m, 24H,
CH(CH3)2, C(CH3)3), 0.03, 0.02, K0.01, K0.07 (4s, 12H,
Si(CH3)2); 13C NMR (100 MHz, CDCl3) d 172.7, 169.3,
162.8, 156.3, 150.6, 143.3, 142.4, 142.3, 136.2, 131.4,
128.5, 128.1, 128.0, 127.5, 124.7, 124.5, 117.5, 102.4, 93.5,
86.8, 74.0, 73.5, 67.0, 66.9, 62.8, 53.4, 48.1, 41.5, 37.9,
28.0, 25.7, 24.6, 23.0, 22.8, 21.9, 18.0, 17.8, K4.5, K4.6,
K4.7, K5.1; FAB HRMS (NBA): m/e 973.4905, MCNaC
calcd for C48H74N6O10Si2 973.4903.
2.1 Hz, 1H, H5), 4.43 (d, JZ4.3 Hz, 1H, H4 ), 4.29 (d, JZ
0
0
1.6 Hz, 1H, H5 ), 4.30 (dd, JZ4.3, 4.3 Hz, 1H, H3 ), 4.12
0
0
(dd, JZ4.8, 4.3 Hz, 1H, H2 ), 3.61 (d, JZ1.6 Hz, 1H, H6 ),
0.91 and 0.88 (2s, 18H, C(CH3)3), 0.13, 0.12, 0.07 and 0.05
(4s, 12H, Si(CH3)2); 13C NMR (100 MHz, CDCl3) d 164.6,
163.1, 150.4, 139.2, 135.5, 130.2, 125.7, 124.6, 123.3,
121.1, 116.4, 111.1, 103.0, 88.2, 78.7, 74.9, 73.3, 57.7, 51.0,
25.7, 25.6, 18.0, 17.9, K4.4, K4.7, K4.9; FAB HRMS
(NBA): m/e 650.2692, MCNaC calcd for C31H45N3O7Si2
650.2694.
4.22. Epoxy acid 41. Reaction of epoxy amide 40 with
lithium hydroxide
4.20. Amine alcohol 39
To a solution of epoxy amide 40 (57 mg, 0.091 mmol,
1.0 equiv) in THF (3 mL) was added a 0.1 M aqueous LiOH
solution (1.82 mL, 0.182 mmol, 2.0 equiv) dropwise during
15 min at 0 8C. After 5 min, the reaction mixture was
diluted with EtOAc (3 mL) and both phases were separated.
The aqueous layer was washed with EtOAc (2!3 mL) and
acidified with Amberlyst-15 until pH 5. Then, the solution
was extracted with EtOAc (3!3 mL) and the combined
organic extracts were concentrated in vacuo to obtain crude
epoxy acid 41 (40 mg, 83%), which did not require further
purification and was used in the next step: RfZ0.1 (silica
gel, 50% AcOEt in hexanes); [a]2D2 C74.9 (c 0.3, CH2Cl2);
1H NMR (400 MHz, CDCl3) d 9.33 (bs, 1H, NH), 7.68 (d,
Compound 38 (31 mg, 0.033 mmol, 1.0 equiv) was dis-
solved in MeOH (3 mL) and purged with Ar. Then, 10%
Pd–C (30 mg) was added and the reaction mixture was
exposed to a H2 atmosphere for 30 min. After this time, the
mixture was filtered and the filtrate was washed with MeOH
(2!3 mL). The combined organic solution was concen-
trated under reduced pressure and the resulting crude
product was purified by flash column chromatography
(silica gel, 10% MeOH in CH2Cl2) to obtain amine 39
(23 mg, 86%) as a white solid: RfZ0.39 (silica gel, 10%
MeOH in CH2Cl2); [a]2D2 K11.3 (c 0.2, CH2Cl2); 1H NMR
(400 MHz, CDCl3) d 8.20 (d, JZ8.1 Hz, 1H, Ar), 7.64 (d,
JZ8.1 Hz, 1H, H6), 7.50 (bs, 1H, NH), 7.17–7.12 (m, 2H,
Ar), 7.01 (dd, JZ7.5, 7.5 Hz, 1H, Ar) 5.67 (d, JZ8.1 Hz,
0
JZ8.1 Hz, 1H, H6), 5.88 (d, JZ4.8 Hz, 1H, H1 ), 5.78 (d,
0
JZ8.1 Hz, 1H, H5), 4.33 (d, JZ4.3 Hz, 1H, H4 ) 4.13–4.09
0
0
0
(m, 1H, H2 ), 4.05 (dd, JZ4.3, 4.3 Hz, 1H, H3 ), 3.64 (d, JZ
1H, H5), 5.61 (d, JZ6.4 Hz, 1H, H1 ), 4.44 (dd, JZ6.4,
0
0
0
5.4 Hz, 1H, H2 ) 4.31 (bs, 1H, H4 ), 4.14–4.08 (m, 3H, H3 ,
0
0
1.6 Hz, 1H, H6 ), 3.46 (bs, 1H, H5 ), 0.91 and 0.86 (2s, 18H,
C(CH3)3), 0.11, 0.10, 0.04, 0.03 (4s, 12H, Si(CH3)2); 13C
NMR (100 MHz, CDCl3) d 176.4, 172.0, 163.7, 139.8,
102.7, 88.3, 78.8, 75.0, 73.3, 57.2, 50.0, 25.8, 25.7, 18.1,
17.9, K4.4, K4.7, K4.9; FAB HRMS (NBA): m/e
551.2223, MCNaC calcd for C23H40N2O8Si2 551.2221.
0
CH2CH2N indoline), 3.84 (d, JZ6.4 Hz, 1H, H5 ), 3.72 (d,
0
JZ6.4 Hz, 1H, H6 ), 3.43–3.21 (m, 3H, CH2NHCO,
CHCH2CH(CH3)2), 3.18–3.12 (m, 2H, CH2CH2N indoline),
2.72–2.68 and 2.53–2.43 (2m, 2H, CH2NH), 1.63–1.61 (m, 4H,
CH2, CHCH2CH(CH3)2, CHCH2CH(CH3)2), 1.32–1.25 (m,
1H, CHCH2CH(CH3)2), 0.89–0.81 (m, 24H, CH(CH3)2,
C(CH3)3), 0.04, 0.02, K0.01, K0.06 (4s, 12H, Si(CH3)2);
13C NMR (100 MHz, CDCl3) d 175.2, 169.5, 163.1, 150.5,
142.8, 142.3, 131.5, 127.5, 124.7, 124.5, 117.5, 102.4, 91.2,
86.1, 73.4, 71.4, 62.4, 53.4, 48.1, 45.2, 43.8, 36.9, 30.9,
29.6, 28.0, 25.8, 25.7, 24.8, 23.2, 21.4, 18.0, 17.9, K4.5,
4.23. t-Butyl epoxy ester 42
To a stirred solution of epoxy acid 41 (35 mg, 0.066 mmol,
1.0 equiv) in CH2Cl2 (3 mL) was added t-Butyl 2,2,2-
trichloroacetimidate 1 M in cyclohexane (0.132 mL,

´
F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11862
0
0
0.132 mmol, 2.0 equiv). After being stirred for 24 h at 25 8C,
the reaction mixture was concentrated under reduced
pressure. Purification by flash column chromatography
(silica gel, 35% EtOAc in hexanes) afforded t-butyl epoxy
ester 42 (38 mg, 98%) as a pale yellow solid impurified with
2,2,2-trichloroacetamide: RfZ0.33 (silica gel, 30% EtOAc
in hexanes); [a]D22 C16.1 (c 0.6, CH2Cl2); 1H NMR
(400 MHz, CDCl3) d 9.39 (bs, 1H, NH), 7.66 (d, JZ
H4 ), 4.14 (dd, JZ4.8, 2.7 Hz, 1H, H3 ), 3.88–3.78 (m, 2H,
0
0
H5 , H6 ), 1.52 (s, 9H, OC(CH3)3), 0.89 and 0.84 (2s, 18H,
C(CH3)3), 0.07, 0.02, and K0.03 (3s, 12H, Si(CH3)2); 13C
NMR (100 MHz, CDCl3) d 169.2, 162.9, 150.4, 142.7,
102.5, 92.6, 84.4, 84.3, 73.4, 72.6, 70.1, 62.3, 28.0, 25.8,
25.7, 18.0, 17.9, K4.5, K4.6, K4.7, K5.0; FAB HRMS
(NBA): m/e 650.3019, MCNaC calcd for C27H49N5O8Si2
650.3017.
0
8.1 Hz, 1H, H6), 5.85 (d, JZ4.3 Hz, 1H, H1 ), 5.76 (dd, JZ
0
8.1, 1.6 Hz, 1H, H5), 4.30 (dd, JZ4.3, 1.1 Hz, 1H, H4 )
4.26. Bromohydrine 45
0
0
4.11–4.08 (m, 1H, H3 ), 4.04 (dd, JZ8.6, 4.3 Hz, 1H, H2 ),
0
3.48 (d, JZ2.1 Hz, 1H, H6 ), 3.34 (dd, JZ2.1, 1.1 Hz, 1H,
H5 ), 1.47 (s, 9H, OC(CH3)3), 0.89 and 0.84 (2s, 18H,
A solution of epoxy amide 33 (0.19 g, 0.302 mmol,
1.0 equiv) in dry and freshly distilled acetone was cooled
to K20 8C and treated with NaBr (0.127 g, 1.2 mmol,
4.0 equiv) and Amberlyst 15 (99 mg, 0.45 mmol,
1.5 equiv). The mixture was kept at K20 8C and vigorously
stirred for 12 h. After that time, the mixture was filtered
through a pad of Celite and washed with acetone (2!5 mL).
The filtrates were concentrated under reduced pressure and
the crude product was purified by flash column chromatog-
raphy (silica gel, 50% EtOAc in hexanes) to provide
bromohydrine 45 (0.214 g, 99%) as a white solid: RfZ0.40
(silica gel, 40% EtOAc in hexanes); [a]2D2 K76.0 (c 0.5,
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 9.25 (bs, 1H, NH),
8.22 (d, JZ8.1 Hz, 1H, Ar), 7.86 (d, JZ8.1 Hz, 1H, H6),
7.22–7.18 (m, 2H, Ar), 7.07 (dd, JZ7.0, 7.0 Hz, 1H, Ar),
5.85 (dd, JZ5.4 Hz, 1H, H1 ), 5.70 (d, JZ8.1 Hz, 1H, H5),
4.55 (d, JZ3.2 Hz, 1H, H4 ), 4.48 (d, JZ9.7 Hz, 1H, H5 ),
4.39 (d, JZ9.7 Hz, 1H, H6 ), 4.34–4.27 (m, 2H, H2 ,
CH2CH2N indoline), 4.18 (dd, JZ3.8, 3.8 Hz, 1H, H3 ),
4.09–4.01 (m, 1H, CH2CH2N indoline), 3.22–3.16 (m, 2H,
CH2CH2N indoline), 0.91 and 0.85 (2s, 18H, C(CH3)3),
0.11, 0.09, 0.03 and K0.004 (4s, 12H, Si(CH3)2); 13C NMR
(100 MHz, CDCl3) d 166.0, 163.3, 150.4, 142.2, 141.3,
131.7, 127.6, 125.1, 124.8, 117.7, 102.4, 89.7, 83.6, 74.7,
72.7, 71.2, 48.0, 43.3, 27.9, 25.8, 25.7, 18.0, 17.9, K4.9,
K4.7, K4.6, K4.9; FAB HRMS (NBA): m/e 732.2117,
MCNaC calcd for C31H48BrN3O7Si2 732.2112.
0
C(CH3)3), 0.1, 0.09, 0.03, 0.02 (4s, 12H, Si(CH3)2); 13C
NMR (100 MHz, CDCl3) d 167.0, 150.1, 139.5, 139.4,
102.8, 88.0, 83.3, 78.9, 74.9, 73.5, 56.8, 50.1, 27.9, 25.8,
25.6, 18.1, 17.9, K4.4, K4.7, K4.8, K4.9; FAB HRMS
(NBA): m/e 607.2845, MCNaC calcd for C27H48N2O8Si2
607.2847.
4.24. Azido alcohol 43
A solution of epoxy ester 42 (95 mg, 0.16 mmol, 1.0 equiv)
in MeOH (3 mL) was treated with a 1.68 M of 1-azido-3-
propanoamine solution in Et2O (0.15 mL, 0.24 mmol,
1.5 equiv). After stirring at 70 8C for 4 days, the crude
mixture was then diluted with toluene (1.0 mL) and
concentrated in vacuo. Purification by flash column
chromatography (silica gel, 40% EtOAc in hexanes)
provided compound 43 (22 mg, 20%) as a white solid:
RfZ0.47 (silica gel, 50% EtOAc in hexanes); [a]2D2 C26.2
(c 0.4, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 7.89 (d, JZ
8.1 Hz, 1H, H6), 5.71 (d, JZ8.1 Hz, 1H, H5), 5.56 (d, JZ
0
0
0
0
0
0
0
0
4.3 Hz, 1H, H1 ), 4.28 (dd, JZ4.3, 4.3 Hz, 1H, H2 ), 4.15–
0
0
0
0
4.02 (m, 4H, H3 , H4 , H5 , H6 ), 3.87 (bs, 1H, OH), 3.37 (m,
2H, CH2N3), 2.91–2.81 and 2.64–2.58 (2m, 2H, CH2NH),
1.77–1.71 (m, 2H, CH2), 1.47 (s, 9H, OC(CH3)3), 0.89 and
0.84 (2s, 18H, C(CH3)3), 0.09, 0.06, 0.04 and 0.03 (4s, 12H,
Si(CH3)2); 13C NMR (100 MHz, CDCl3) d 162.8, 150.0,
141.7, 141.6, 102.1, 92.1, 84.2, 74.0, 71.9, 68.7, 64.2, 57.2,
49.4, 45.9, 29.7, 28.0, 25.8, 25.7, 18.0, 17.9, K4.3, K4.7,
K4.8, K4.9; FAB HRMS (NBA): m/e 707.3602, MCNaC
calcd for C30H56N6O8Si2 707.3596.
4.27. Bromohydrine 47. Oxidation of bromohydrine 45
with DMP and reduction of ketone 46 with NaBH4
To a stirred solution of bromohydrine 45 (0.184 g,
0.259 mmol, 1.0 equiv) in CH2Cl2 (3 mL) was added
DMP (0.226 g, 0.518 mmol, 2.0 equiv) at 0 8C. The reaction
mixture was then stirred for 8 h with complete depletion of
starting material according to TLC chromatography. The
crude mixture was diluted with CH2Cl2 (10 mL) and washed
with saturated aqueous NaHCO3 solution (10 mL). The
aqueous solution was extracted with CH2Cl2 (2!10 mL)
and the combined organic phase was washed with brine
(10 mL), dried over MgSO4 and concentrated under reduced
pressure to obtain ketone 46, which was used in the next step
without purification.
4.25. Azido alcohol 44
A solution of epoxy ester 42 (53 mg, 0.091 mmol,
1.0 equiv) in DMF (2 mL) was treated with sodium azide
(11.8 mg, 0.181 mmol, 2.0 equiv) and the mixture was
heated until 658. After stirring for 3 h, the solution was
allowed to reach room temperature, diluted with Et2O
(5 mL) and washed with saturated aqueous NH4Cl solution
(5 mL). The aqueous solution was extracted with Et2O (2!
2 mL) and the combined organic phase was washed with
brine (4 mL), dried over MgSO4 and concentrated under
reduced pressure. The crude mixture was purified by flash
column chromatography (silica gel, 40% EtOAc in hexanes)
to provide azido alcohol 44 (47 mg, 83%) as a white solid:
RfZ0.72 (silica gel, 50% EtOAc in hexanes); [a]2D2 C10.1
(c 0.8, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 9.07 (bs, 1H,
NH), 7.64 (d, JZ8.1 Hz, 1H, H6), 5.74 (d, JZ8.1, 2.1 Hz,
To a solution of the obtained ketone 46 (0.151 g,
0.213 mmol, 1.0 equiv) in EtOH (3 mL) was slowly added
NaBH4 (8.39 mg, 0.213 mmol, 1.0 equiv) at 0 8C. After
stirring for 1 h 15 min, the reaction mixture was diluted with
EtOAc (5 mL) and washed with H2O (5 mL) and brine
(5 mL). The combined organic phases were dried over
MgSO4 and concentrated in vacuo. Purification by flash
column chromatography (silica gel, 30/50% EtOAc in
0
1H, H5), 5.57 (d, JZ5.9 Hz, 1H, H1 ), 4.45 (dd, JZ5.9,
0
4.8 Hz, 1H, H2 ), 4.26 (d, JZ6.4 Hz, 1H, OH), 4.20 (bs, 1H,

´
F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11863
hexanes) provided pure syn bromohydrine 47 (56.7 mg
38%), anti bromohydrine 45 (7.8 mg, 5%), and a more polar
fraction of unknown products (58.5 mg).
saturated aqueous NH4Cl solution (2!10 mL). The
combined organic phases were dried over MgSO4 and
concentrated in vacuo. Purification by flash column
chromatography (silica gel, 60% EtOAc in hexanes)
afforded the corresponding coupling product (0.157 g,
91%) as a white solid: RfZ0.45 (silica gel, 60% EtOAc in
hexanes); [a]2D2 K20.6 (c 0.5, CH2Cl2); 1H NMR (400 MHz,
CDCl3) d 7.32–7.29 (m, 5H, aromatics Cbz), 6.78 (bs, 1H,
NH), 5.50 (br s, 1H, NHCbz), 5.06 (bs, 2H, CH2Ar), 5.00
(bs, 1H, NHBoc), K4.06 (bs, 1H, CHCH2CH(CH3)2), 3.27–
3.25 and 3.19–3.16 (2m, 4H, CH2NHC(O)O, CH2NHCO),
1.63–1.57 (m, 5H, CH2, CHCH2CH(CH3)2, CHCH2-
CH(CH3)2), 1.40 (s, 9H, C(CH3)3), 0.91–0.88 (m, 6H,
CH(CH3)2); 13C NMR (100 MHz, CDCl3) d 173.4, 156.8,
155.8, 136.5, 128.4, 127.9, 80.1, 66.5, 53.2, 41.3, 37.3, 35.8,
29.8, 28.2, 24.7, 22.8, 21.9.
Compound [47]: White solid: RfZ0.51 (silica gel, 40%
EtOAc in hexanes); [a]2D2 K75.5 (c 1.2, CH2Cl2); 1H NMR
(400 MHz, CDCl3) d 8.71 (bs, 1H, NH), 8.17 (d, JZ8.1 Hz,
1H, Ar), 7.22–7.18 (m, 2H, Ar), 7.15 (d, JZ8.1 Hz, 1H, H6),
7.07 (dd, JZ7.0, 7.0 Hz, 1H, Ar), 5.66 (dd, JZ8.1, 2.2 Hz,
0
1H, H5), 5.27 (d, JZ8.1 Hz, 1H, H1 ), 5.08 (bs, 1H, OH),
0
0
4.83 (dd, JZ8.1, 4.3 Hz, 1H, H2 ), 4.78 (bs, 1H, H4 ), 4.35
0
(d, JZ4.3 Hz, 1H, H3 ), 4.29–4.23 (m, 1H, CH2CH2N
0
indoline), 4.12–4.01 (m, 2H, H5 , CH2CH2N indoline), 3.93
0
(d, JZ9.1 Hz, 1H, H6 ), 3.23–3.19 (m, 2H, CH2CH2N
indoline), 0.92 and 0.81 (2s, 18H, C(CH3)3), 0.16, 0.12, 0.01
and K0.10 (4s, 12H, Si(CH3)2); 13C NMR (100 MHz,
CDCl3) d 168.3, 163.1, 149.7, 144.9, 141.9, 131.9, 127.6,
124.7, 125.0, 117.8, 102.0, 96.0, 86.2, 73.3, 70.7, 70.2, 48.0,
46.2, 27.9, 25.8, 25.7, 18.0, 17.9, K4.5, K4.6, K4.8, K5.3;
FAB HRMS (NBA): m/e 732.2117, MCNaC calcd for
C31H48BrN3O7Si2 732.2112.
A solution of coupling product (0.113 g, 0.268 mmol,
1.0 equiv) in MeOH (3 mL) was purged with Ar. Then, a
10% Pd–C (113 mg) was added, and the mixture was allowed
to be exposed to a H2 atmosphere and stirred for 40 min. After
this time, the mixture was filtered and the filtrate was washed
with MeOH (2!5 mL). The combined organic solution was
dried (MgSO4), and concentrated under reduced pressure to
obtain the corresponding free amine 49 (69 mg, 90%), which
was used in the next step without purification.
4.28. Epoxy amide 48
Syn bromohydrine 47 (43 mg, 0.06 mmol, 1.0 equiv) was
treated with a 0.1 M NaOMe solution in MeOH (1.8 mL,
0.18 mmol, 3.0 equiv) at room temperature and the mixture
was stirred for 24 h. After that, the solvent was concentrated
under reduced pressure and the crude product was purified
by flash column chromatography (silica gel, 50% EtOAc in
hexanes) to obtain cis epoxy amide 48 (38 mg, 99%) as a
white solid: RfZ0.30 (silica gel, 40% EtOAc in hexanes);
[a]2D2 C8.9 (c 0.1, CH2Cl2); 1H NMR (400 MHz, CDCl3) d
8.79 (bs, 1H, NH), 8.16 (d, JZ8.1 Hz, 1H, Ar), 7.13 (d, JZ
8.1 Hz, 1H, H6), 7.20–7.16 (m, 2H, Ar), 7.03 (dd, JZ7.0,
7.0 Hz, 1H, Ar), 5.65 (dd, JZ8.1, 2.2 Hz, 1H, H5), 5.30 (d,
4.30. Amino alcohol 50
Epoxy amide 48 (34 mg, 0.054 mmol, 1.0 equiv) was
dissolved in MeOH (1.5 mL) and amine 49 (62 mg,
0.216 mmol, 4.0 equiv) was added. After stirring at 70 8C
for 14 days, the solvent was concentrated under reduced
pressure and the crude product was purified by flash column
chromatography (silica gel, 75% EtOAc in hexanes) to give
amino alcohol 50 (34 mg, 97%) and 10 mg of starting
material [50]: white solid: RfZ0.29 (silica gel, 70% EtOAc in
0
0
JZ7.5 Hz, 1H, H1 ), 4.95 (dd, JZ7.5, 4.3 Hz, 1H, H2 ), 4.28
(d, JZ4.3 Hz, 1H, H3 ), 4.17–4.07 (m, 2H, CH2CH2N
indoline), 3.86 (d, JZ8.1 Hz, 1H, H4 ), 3.79 (d, JZ4.3 Hz,
hexanes); [a]2D2 C4.5 (c 0.2, CH2Cl2); H NMR (400 MHz,
1
0
0
CDCl3) d 8.16 (d, JZ8.1 Hz, 1H, Ar), 7.38 (d, JZ7.5 Hz,
1H, H6), 7.16–7.12 (m, 2H, Ar), 7.01 (dd, JZ7.5, 7.5 Hz, 1H,
0
0
1H, H6 ), 3.62 (dd, JZ8.1, 4.3 Hz, 1H, H5 ), 3.17–3.13 (m,
2H, CH2CH2N indoline), 0.86 and 0.82 (2s, 18H, C(CH3)3),
0.1, 0.08, 0.03 and K0.05 (4s, 12H, Si(CH3)2); 13C NMR
(100 MHz, CDCl3) d 162.9, 149.7, 144.0, 142.3, 130.9,
127.5, 124.5, 124.3, 117.1, 102.2, 95.1, 83.1, 74.2, 71.3,
55.4, 54.4, 46.5, 28.2, 25.6, 25.5, 17.9, 17.8, K4.6, K4.8,
K4.9, K5.2; FAB HRMS (NBA): m/e 652.2847, MCNaC
calcd for C31H47N3O7Si2 652.2850.
0
Ar), 6.85 (bs, 1H, NHCO), 5.73 (d, JZ6.4 Hz, 1H, H1 ), 5.52
(d, JZ7.5 Hz, 1H, H5), 5.00 (bs, 1H, NHBoc), 4.37–4.27 (m,
0
3H, H3 , H4 , CH2CH2N indoline), 4.23 (br s, 1H, H2 ), 4.06–
0
0
0
3.95 (m, 3H, H5 , CH2CH2N indoline, CHCH2CH(CH3)2),
0
3.87 (bs, 1H, H6 ), 3.54 (bs, 1H, NH), 3.40 and 3.25 (2bs, 2H,
CH2NHCO), 3.13 (bs, 2H, CH2CH2N indoline), 2.79
and 2.50 (2bs, 2H, CH2NH), 1.71–1.53 (m, 4H, CH2,
CHCH2CH(CH3)2, CHCH2CH(CH3)2), 1.44–1.41 (m, 1H,
CHCH2CH(CH3)2), 1.41 (s, 9H, OC(CH3)3), 0.90 and 0.77
(2s, 18H, C(CH3)3), 0.89–0.83 (m, 6H, CH(CH3)2), 0.12,
K0.08, K0.002 and K0.07 (4s, 12H, Si(CH3)2); 13C NMR
(100 MHz, CDCl3) d 172.5, 172.0, 162.8, 155.9, 150.2,
142.0, 141.6, 131.7, 127.4, 124.7, 124.6, 117.7, 102.3, 89.3,
86.2, 80.1, 73.4, 72.5, 71.3, 62.3, 53.0, 48.2, 45.3, 40.8, 37.3,
29.7, 28.3, 25.8, 25.6, 24.6, 22.8, 18.1, 17.8, K4.5, K4.7,
K4.8; FAB HRMS (NBA): m/e 939.5065, MCNaC calcd
for C45H76N6O10Si2 939.5059.
4.29. Amine 49
To a solution of Boc-Leu-OH (0.11 g, 0.48 mmol,
1.2 equiv) in CH2Cl2 (3 mL) was added HOBt (66 mg,
0.48 mmol, 1.2 equiv) and the mixture was stirred for 5 min.
After that time, EDCI (94 mg, 0.48 mmol, 1.2 equiv) was
added and the reaction mixture was stirred for 45 min at
room temperature. The resulting mixture was added to a
solution of N-Z-1,3-diaminopropane hydrochloride (0.1 g,
0.4 mmol, 1.0 equiv) in MeOH (2 mL), which was
previously treated with triethylamine (0.22 mL, 1.6 mmol,
4.0 equiv) for 30 min at room temperature. The reaction
mixture was stirred at room temperature for 1 h 10 min, and
then, a 15% aqueous NH3 solution (0.5 mL) was added. The
mixture was diluted with ether (10 mL) and washed with a
4.31. Amino alcohol 51
Epoxy amide 33 (52 mg, 0.083 mmol, 1.0 equiv) was
dissolved in MeOH (2 mL) and amine 49 (53 mg,
0.183 mmol, 2.2 equiv) was added. The mixture was heated

´
F. Sarabia, L. Martın-Ortiz / Tetrahedron 61 (2005) 11850–11865
11864
Ikeda, Y.; Kagami, S.; Yoshihama, M.; Ubukata, M.; Esumi,
Y.; Osada, H.; Isono, K. J. Antibiot. 1998, 51, 647–654.
7. Ochi, K.; Ezaki, M.; Iwani, M.; Komori, T.; Kohsaka, M. Ep
Patent 333177, 1989.
until 70 8C and stirred for 4 days. After this time, the solvent
was concentrated under reduced pressure and the crude
product was purified by flash column chromatography
(silica gel, 50% EtOAc in hexanes /10% MeOH in
CH2Cl2) to give amino alcohol 51 (59.1 mg, 99%) together
with unreacted starting material (11 mg [51]): pale yellow:
RfZ0.48 (silica gel, 10% MeOH in CH2Cl2); [a]2D2 –17.3
8. Igarashi, M.; Nakagawa, N.; Doi, S.; Hattori, N.; Naganawa,
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Biochemistry 1966, 5, 82–93.
1
(c 0.4 CH2Cl2); H NMR (400 MHz, CDCl3) d 9.40 (br s,
1H, NH), 8.21 (d, JZ8.6 Hz, 1H, Ar), 7.56 (d, JZ8.1 Hz,
1H, H6), 7.17–7.14 (m, 2H, Ar), 7.01 (dd, JZ7.0, 7.0 Hz,
1H, Ar), 6.69 (bs, 1H, NHCO), 5.66 (d, JZ8.1 Hz, 1H, H5),
10. McDonald, L. A.; Barbieri, L. R.; Carter, G. T.; Lenoy, E.;
Lotvin, J.; Petersen, P. J.; Siegel, M. M.; Singh, G. Abstract of
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Takatsuki, A. J. Antibiot. 1997, 50, 103–104. (c) Kimura,
K.-I.; Ikeda, Y.; Kagami, S.; Yoshihama, M.; Suzuki, K.;
Osada, H.; Isono, K. J. Antibiot. 1998, 51, 1099–1104.
12. McDonald, L. A.; Barbieri, L. R.; Carter, G. T.; Lenoy, E.;
Lotvin, J.; Petersen, P. J.; Siegel, M. M.; Singh, G.;
Williamson, R. T. J. Am. Chem. Soc. 2002, 124, 10260–10261.
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B. A.; Singh, G.; Yang, Y.; Mansour, T. S.; Ho, D. M. Bioorg.
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0
5.53 (d, JZ5.9 Hz, 1H, H1 ), 4.99 (bs, 1H, NHBoc), 4.54
0
(bs, 1H, H2 ), 4.30 (bs, 1H, H4 ), 4.15–4.06 (m, 4H, H3 ,
0
0
CH2CH2N indoline, CHCH2CH(CH3)2), 3.82 (d, JZ6.4 Hz,
0
0
1H, H5 ), 3.73–3.69 (m, 1H, H6 ), 3.38–3.23 (m, 2H,
CH2NHCO), 3.19–3.13 (m, 2H, CH2CH2N indoline), 2.80–
2.71 and 2.43–2.33 (2m, 2H, CH2NH), 1.67–1.51 (m, 4H,
CH2, CHCH2CH(CH3)2, CHCH2CH(CH3)2), 1.42–1.38 (m,
1H, CHCH2CH(CH3)2), 1.40 (s, 9H, OC(CH3)3), 0.91–0.81
(m, 24H, CH(CH3)2, C(CH3)3), 0.03, K0.005, K0.013 and
K0.08 (4s, 12H, Si(CH3)2); 13C NMR (100 MHz, CDCl3) d
172.9, 171.9, 162.7, 155.9, 150.6, 143.4, 142.3, 131.4,
127.5, 124.7, 124.5, 117.5, 102.4, 93.8, 86.9, 80.1, 77.2,
73.6, 72.4, 63.0, 52.8, 48.1, 45.7, 41.4, 37.9, 29.7, 28.3,
28.0, 25.7, 25.6, 24.7, 22.9, 21.9, 18.0, 17.9, K4.6, K4.7,
K5.1; FAB HRMS (NBA): m/e 939.5072, MCNaC calcd
for C45H76N6O10Si2 939.5059.
14. Danishefsky, S. J.; DeNinno, S. L.; Chen, S.-H.; Boisvert, L.;
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R. A.; Singh, G.; Yang, Y.; Mansour, T. S.; Ho, D. M. Bioorg.
Med. Chem. Lett. 2002, 12, 2341–2344.
Acknowledgements
´
This work was financially supported by Fundacion Ramon
Areces and the Direccion General de Investigacion y
´
´
´
16. DeMong, D. E.; Williams, R. M. J. Am. Chem. Soc. 2003, 125,
8561–8565.
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Cientıfica Tecnica (Ref. BQU2001-1576). L. M. O. thanks
the Direccion General de Universidades e Investigacion,
´
´
´
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´ ´
18. Sarabia, F.; Martın-Ortiz, L.; Lopez-Herrera, F. J. Org. Lett.
´
´
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Consejerıa de Educacion y Ciencia, Junta de Andalucıa for a
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preparation of this manuscript. We thank Unidad de
2003, 5, 3927–3930.
´
Espectroscopıa de Masas de la Universidad de Granada
for exact mass spectroscopic assistance.
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