Tri-, tetra- and pentapeptidoylbenzotriazoles: Novel synthetic intermediates

Article abstract of DOI:10.1055/s-0030-1260159

Conveniently synthesized novel N-(protected α-tri-, tetra- and pentapeptidoyl)benzotriazoles couple in aqueous aceto-nitrile solution at 0C with free amino acids, dipeptides, and tripeptides- to afford N-terminal-protected polypeptides (61-92%) including

Full text of DOI:10.1055/s-0030-1260159

PAPER
2995
Tri-, Tetra- and Pentapeptidoylbenzotriazoles: Novel Synthetic Intermediates
T
ri-,
T
etra- and Pe
b
ntapeptidoyl
d
benzotriazole
e
s
lmotaal Abdelmajeid,a,b Srinivasa R. Tala,a M. S. Amine,b Alan R. Katritzky*a,c
a
Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA
Fax +1(352)3929199; E-mail: katritzky@chem.ufl.edu
b
c
Department of Chemistry, Faculty of Science, Benha University, Benha 13518, Egypt
Chemistry Department, King Abdulaziz University, Jeddah 21589, Saudi Arabia
Received 13 June 2011
O
Abstract: Conveniently synthesized novel N-(protected a-tri-,
tetra- and pentapeptidoyl)benzotriazoles couple in aqueous aceto-
nitrile solution at 0 °C with free amino acids, dipeptides, and
tripeptides to afford N-terminal-protected polypeptides (61–92%)
including those containing unprotected OH, SH, and indole NH
groups, with no detectable racemization.
NH
O
NH
O
H3CO
O
N
Me
N
Me
O
N
HN
Me
O
Key words: acylation, peptides, coupling, amino acids, medicinal
O
chemistry
OCH3
Figure 1 Cyclic hexapeptide RA-VII
Over 40 peptides are available as pharmaceuticals and
more than 100 others are in clinical trials.1 Peptides and
their derivatives are used extensively in the field of medi-
cine as anticancer drug carriers,2 as probes for molecular
imaging and disease diagnosis,3 and they play important
roles in drug design and discovery.4 Several peptides
showed antibacterial activity,5 and naturally occurring an-
tibiotic peptides play a role as effectors of innate immuni-
ty.6 Many naturally occurring tetra-, penta-, hexa-, and
other polypeptides with molecular weights in the range of
530–840 Da are biologically active. For example, linear
tetrapeptide belamide A, from the marine cyanobacterium
Symploca sp., exhibits classic tubulin destabilizing anti-
mitotic characteristics;7a dolastatins 10 and 15 from the
sea-hare Dolabella auricularia display extraordinary cy-
totoxicity towards cancer cells (IC50 value 2.9 nM),7b,c and
S–S tetrapeptides show high affinity and selectivity for
the m-opioid receptor and show antioxidant properties to-
wards mitochondria.8 Other tetrapeptides are potent
against recombinant BACE1 (b-site amyloid precursor
protein cleaving enzyme 1), up to an IC50 value of
34.6 nM from KMI-927.9 BACE1, which is involved in
amyloid b-peptide production in Alzheimer’s disease, is a
major target for current drug design. Synthetic potent an-
timicrobial hexapeptides have great potential for basic re-
search and drug discovery.10
laughlini, display growth-suppressive activity against di-
verse cancer cell lines.13
Efficient syntheses of peptides and their conjugates need
(i) high yields, (ii) fast reactions, and (iii) preservation of
chirality. Coupling reagents used in the synthesis of bio-
logically active peptides and their analogues include: (i)
carbodiimides (DCC, DIC, EDC),14,15 in combination
with additives such as 1-hydroxybenzotriazole
(HOBt),16,17 1-hydroxy-7-aza-benzotriazole (HOAt), and
analogues;18 (ii) phosphonium (PyBOP, HPyOPfp)19–21
and uronium salts22,23 of HOBt or HOAt; (iii) 1H-benzim-
idazolium type coupling reagent (CMBI);24 (iv) mixed an-
hydrides,25 or (v) carboxylic acid fluorides.22 However,
most protocols using these coupling reagents require prior
protection and subsequent deprotection of various amino
acid functional groups, exclusion of moisture, and usually
involve column chromatographic isolation from by-prod-
ucts.
Tetra-, penta-, hexa- and longer peptides are usually pre-
pared using solid-phase peptide synthesis (SPPS)26–31 or
enzymatic synthesis,32,33 but many of these techniques
suffer from low overall yields and are typically unsuitable
for large-scale reactions (see conclusion section).
N-(Protected a-aminoacyl)benzotriazoles or N-(protected
a-dipeptidoyl)benzotriazoles were previously reported to
be effective reagents for the synthesis of di-, tri-, and
tetrapeptides.34,35 We now demonstrate the use of novel N-
(protected tri-, tetra- and pentapeptidoyl)benzotriazoles as
advantageous laboratory bench coupling reagents for the
synthesis of tetra-, penta-, hexa-, and heptapeptides. Our
N-(protected tri-, tetra- and pentapeptidoyl)benzotria-
zoles: (i) form amide bonds easily at low temperatures;
(ii) can be stored in the crystalline state at room tempera-
ture for at least five months; (iii) provide products in good
yields with no detectable racemization; (iv) are prepared
from commercially available and inexpensive reagents,
and (iv) are easily purified (no HPLC required).
Cyclic hexapeptide RA-VII (Figure 1), extracted from
Rubiae radix, exhibits antitumor activity,11a causes a con-
formational change in the actin molecule and induces G2
arrest by inhibiting cytokinesis;11b Ceratospongamides are
bioactive cyclic heptapeptides isolated from the Indone-
sian red alga Ceratodictyon spongiosum and symbiotic
sponge Sigmadocia symbiotica;12 rolloamides A and B,
extracted from the caribbean marine sponge eurypon
SYNTHESIS 2011, No. 18, pp 2995–3005
x
x.
x
x
.
2
0
1
1
Advanced online publication: 23.08.2011
DOI: 10.1055/s-0030-1260159; Art ID: M61111SS
© Georg Thieme Verlag Stuttgart · New York

2996
A. Abdelmajeid et al.
PAPER
Table 1 Preparation of N-(Pg-a-tripeptidoyl)benzotriazoles 2a–f
O
R2
O
O
R2
O
H
H
H
H
N
N
Bt-H
N
N
Pg
N
OH
Pg
N
Bt
H
H
R1
O
R3
R1
O
R3
SOCl2, THF
1a–f
2a–f
Entry
Pg
R1
R2
R3
Product 2
Yield (%)
Mp (°C)
1
2
3
4
5
6
Cbz
Cbz
Cbz
Fmoc
Cbz
Cbz
Me
Bn
Bn
Bn
Me
Me
Bn
H
H
H
2a
2b
2c
2d
2e
2f
Cbz-L-Ala-L-Phe-Gly-Bt
Cbz-L-Phe-Gly-Gly-Bt
80
80
73
76
86
81
186–187
137–139
190–192
162–164
175–176
188–189
Me
Me
i-Pr
Me
Me
Cbz-L-Phe-L-Ala-L-Ala-Bt
Fmoc-L-Phe-L-Ala-L-Val-Bt
Cbz-L-Ala-L-Leu-L-Ala-Bt
Cbz-L-Ala-L-Met-L-Ala-Bt
Me
i-Bu
MeS(CH2)2
N-(Protected a-tripeptidoyl)benzotriazoles, N-(protected N-(Pg-a-Tetrapeptides) 4a–l were prepared in yields of
a-tetrapeptidoyl)benzotriazoles, and N-(protected a-pen- 70–92% by peptide coupling between N-(Cbz- or Fmoc-
tapeptidoyl)benzotriazoles are relatively insensitive to tripeptidoyl)benzotriazoles 2a–f and amino acids 3a–i in
water, indeed, we now use these reagents in aqueous solu- aqueous acetonitrile in the presence of triethylamine at
tion as efficient peptide coupling reagents for the prepara- 0 °C (Table 2). These amino acids include L-Cys-OH hav-
tion of tetra-, penta-, hexa, and heptapeptides on a ing a free SH group, L-Ser-OH with a free hydroxy group,
relatively large scale. Preliminary experiments indicate L-Trp-OH with a free NH group, and L-Met-OH. Reten-
that these reagents will be useful for the introduction of tion of enantiopurity of the product 4i was confirmed by
peptide fragments into diverse scaffolds by reactions with chiral HPLC analysis using a Chirobiotic T column (de-
N-, O-, S- and C-nucleophiles.
tection at 254 nm, flow rate 1 mL/min, and MeOH as the
eluting solvent). The diastereomer 4i showed a single re-
tention-time peak in chiral HPLC at 2.32 min, whereas the
corresponding diastereomeric mixture (4i + 4i¢) showed
two peaks at 2.32 and 2.47 min.
Treatment of N-(Cbz- or Fmoc)tripeptides 1a–f34,36 with
four equivalents of benzotriazole and one equivalent of
thionyl chloride in tetrahydrofuran or dichloromethane at
–45 °C for four hours, gave N-(protected a-tripepti-
doyl)benzotriazoles 2a–f in 73–86% yield (Table 1). The Treatment of N-(Cbz-a-tripeptidoyl)benzotriazoles 2a–c
1
crystalline products 2a–f were characterized by H and with unprotected dipeptides Gly-L-Ala-OH (5a) and Gly-
13C NMR spectroscopy and by elemental analyses. They L-Leu-OH (5b) in aqueous acetonitrile at 0 °C gave N-
are stable at 20 °C for at least five months.
Cbz-pentapeptides 6a–c in 73–81% yield; the products
were characterized by 1H, 13C NMR spectroscopy and by
elemental analysis (Scheme 1).
R4
O
HN
O
R2
O
HO
O
R2
O
R4
O
H
H
Et3N
+
N
N
O
H
H
H
Cbz
N
Bt
N
N
N
H2N
H
CH3CN-H2O
Cbz
N
N
OH
R1
O
R3
R5
H
H
R1
O
R3
6a–c
O
R5
5a,b
2a–c
6a: R1 = Me, R2 = Bn, R3 = H, R4 = H, R5 = Me, 73%
6b: R1 = Bn, R2 = H, R3 = H, R4 = H, R5 = i-Bu, 79%
6c: R1 = Bn, R2 = Me, R3 = Me, R4 = H, R5 = i-Bu, 81%
Scheme 1 Preparation of N-(Cbz-a-pentapeptides) 6a–c from N-(Cbz-a-tripeptidoyl)benzotriazoles 2a–c and unprotected dipeptides 5a and
5b
O
R2
O
R4
O
R2
O
R4
H
H
Bt-H
H
H
N
N
Bt
N
N
OH
Pg
N
N
Pg
N
N
H
H
SOCl2, THF
R1
O
R3
7a–d
O
H
H
R1
O
R3
4b,g,i,j
O
7a: R1 = Me, R2 = Bn, R3 = H, R4 = Me, 75%
7b: R1 = Bn, R2 = Me, R3 = i-Pr, R4 = i-Bu, 78%
7c: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me, 84%
7d: R1 = Me, R2 = MeS(CH2)2, R3 = Me, R4 = Me, 86%
Scheme 2 N-(Pg-a-Tetrapeptidoyl)benzotriazoles 7a–d (for details, see the experimental section)
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

PAPER
Tri-, Tetra- and Pentapeptidoylbenzotriazoles
2997
Table 2 Preparation of N-(Pg-a-tetrapeptides) 4a–l from N-(Pg-a-tripeptidoyl)benzotriazoles 2a–f and Unprotected Amino Acids
R2
O
O
R2
O
R4
O
O
OH
R4
H
H
H
H
Et3N
N
N
N
N
OH
Pg
N
Bt
+
Pg
N
N
H
H
H
H2N
R1
O
R3
MeCN–H2O
R1
O
R3
O
2a–f
3a–i, (3b+3b')
4a–l, (4i+4i')
2
3
Product
4a
Yield (%)
2a
2a
2b
2b
2c
2c
2d
2d
2e
2e
2f
3a
3b
3c
3d
3e
3f
L-Ile-OH
L-Ala-OH
L-Trp-OH
L-Val-OH
L-Met-OH
L-Asp-OH
L-Leu-OH
L-Met-OH
L-Ala-OH
DL-Ala
Cbz-L-Ala-L-Phe-Gly-L-Ile-OH
Cbz-L-Ala-L-Phe-Gly-L-Ala-OH
Cbz-L-Phe-Gly-Gly-L-Trp-OH
Cbz-L-Phe-Gly-Gly-L-Val-OH
Cbz-L-Phe-L-Ala-L-Ala-L-Met-OH
Cbz-L-Phe-L-Ala-L-Ala-L-Asp-OH
Fmoc-L-Phe-L-Ala-L-Val-L-Leu-OH
Fmoc-L-Phe-L-Ala-L-Val-L-Met-OH
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-OH
Cbz-L-Ala-L-Leu-L-Ala-DL-Ala-OH
Cbz-L-Ala-L-Met-L-Ala-L-Ala-OH
Cbz-L-Ala-L-Phe-Gly-L-Cys-OH
Cbz-L-Phe-Gly-Gly-L-Ser-OH
75
86
80
83
76
70
90
88
88
85
92
82
72
4b
4c
4d
4e
4f
3g
3e
3b
4g
4h
4i
(3b+3b¢)
(4i+4i¢)
4j
3b
3h
3i
L-Ala-OH
L-Cys-OH
L-Ser-OH
2a
2b
4k
4l
N-(Pg-a-Tetrapeptidoyl)benzotriazoles 7a–d were pre- (9a)36 in aqueous acetonitrile at 0 °C; the product was
1
pared in 75–86% yields by treatment of N-(Cbz- or characterized by H, 13C NMR spectroscopy and by
Fmoc)tetrapeptides 4b, 4g, 4i, and 4j with four equiva- HRMS analysis (Scheme 4).
lents of benzotriazole and one equivalent of thionyl
chloride in either tetrahydrofuran or dichloromethane at
–20 °C for four hours (Scheme 2).
To illustrate the synthetic utility of our tetrapeptidoyl ben-
zotriazoles, we prepared N-protected hexapeptides 11a–d
by coupling N-(Pg-tetrapepeptidoyl)benzotriazoles 7a–d
Treatment of N-(Cbz-a-tetrapeptidoyl)benzotriazoles 7a with unprotected dipeptides 5a–c in aqueous acetonitrile
and 7c with free amino acids 3b and 3i in aqueous aceto- at 0 °C in 80–87% yield (Table 3). Two of these com-
nitrile at 0 °C gave N-Cbz-pentapeptides 8a and 8b (83– pounds (11c and 11d) were previously prepared by
1
86%), which were characterized by H, 13C NMR spec- Bordusa and co-workers using enzymatic peptide
troscopy and by elemental analysis (Scheme 3).
synthesis32 consisting of three steps: (i) preparation of a
peptide thioester as acyl donor; (ii) preparation of a free
amino peptide segment (using solid-phase synthesis pro-
tocols) as acyl acceptor, and finally (iii) peptide coupling
of the acyl donor and acyl acceptor using enzymatic catalysis.
N-Cbz-Hexapeptide 10 was synthesized in 61% yield by
coupling the N-(Cbz-a-tripeptidoyl)benzotriazole 2c with
previously prepared tripeptide Gly-Leu-Cys(S-Fm)-OH
O
R2
O
R4
H2N
R5
O
H
H
N
N
Bt
+
Cbz
N
N
H
S-Fm
H
O
O
OH
R1
O
R3
O
O
HN
H
H
N
N
H2N
OH
Cbz
N
H
Bt
3b: R5 = Me
3j: R5 = Bn
7a,c
+
NH
O
O
Bn
O
O
2c
9a
R2
O
R4
O
H
N
H
H
N
N
S-Fm
OH
Et3N
MeCN–H2O
Cbz
N
H
N
OH
O
O
O
H
H
H
N
H
R1
O
R3
O
R5
N
N
Et3N
MeCN–H2O
Cbz
N
H
N
H
N
8a: R1 = Me, R2 = Bn, R3 = H, R4 = Me, R5 = Bn, 83%
8b: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me, R5 = Me, 86%
H
Bn
O
O
O
10, 61%
Scheme 3 Preparation of N-Cbz-a-pentapeptides 8a and 8b from N-
(Cbz-a-tetrapeptidoyl)benzotriazoles 7a and 7c, and free amino acids
3b and 3i
Scheme 4 Preparation of N-(Cbz-a-hexapeptide) 10 from N-(Cbz-
a-tripeptidoyl)benzotriazole 2c and tripeptide 9a
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

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Table 3 Preparation of N-(Pg-a-Hexapeptides) 11a–d from N-(Pg-a-Tetrapeptidoyl)benzotriazoles 7a–d and Unprotected Dipeptides 5a–c
R2
O
R4
R5
O
HN
HO
O
R2
O
R4
O
R6
O
H
H
H
H
H
Et3N
O
N
N
Bt
N
N
N
OH
+
Pg
N
N
Pg
N
N
N
H2N
H
H
H
H
H
MeCN–H2O
R1
O
R3
O
R1
O
R3
O
R5
O
R6
5a–c
7a–d
11a–d
7a: R1 = Me, R2 = Bn, R3 = H, R4 = Me
11a: R1 = Me, R2 = Bn, R3 = H, R4 = Me, R5 = H, R6 = i-Bu
7b: R1 = Bn, R2 = Me, R3 = i-Pr, R4 = i-Bu
7c: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me
11b: R1 = Bn, R2 = Me, R3 = i-Pr, R4 = i-Bu, R5 = H, R6 = Me
11c: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me, R5 = Me, R6 = H
7d: R1 = Me, R2 = MeS(CH2)2, R3 = Me, R4 = Me
11d: R1 = Me, R2 = MeS(CH2)2, R3 = Me, R4 = Me, R5 = Me, R6 = H
7
Dipeptide 5
Product 11
11a
Yield (%) Lit. yield (%)
7a
7b
7c
7d
5b
5a
5c
5c
Gly-L-Leu-OH
Gly-L-Ala-OH
L-Ala-Gly-OH
L-Ala-Gly-OH
Cbz-L-Ala-L-Phe-Gly-L-Ala-Gly-L-Leu-OH
80
82
87
84
–
11b
Fmoc-L-Phe-L-Ala-L-Val-L-Leu-Gly-L-Ala-OH
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-Gly-OH
Cbz-L-Ala-L-Met-L-Ala-L-Ala-L-Ala-Gly-OH
–
11c
6728
7128
11d
1
The procedure developed by Bordusa32 includes (i) pep- Products 8a and 8b were characterized by H and 13C
tide coupling reactions using solutions of concentrations NMR spectroscopy and by elemental analysis.
10–8 to 10–7 M for acyl donors, 3 × 10–6 to 1.5 × 10–5 M for
We also prepared N-Cbz-hexapeptide 13 via another route
by coupling N-(Cbz-pentapepeptidoyl)benzotriazoles
(12b) with L-Phe-OH (3j) in aqueous acetonitrile at 0 °C
in 85% yield (Scheme 6).
enzymes, with acyl acceptor concentration and amounts
of solution unspecified; (ii) reaction times of 16 to 120
hours; (iii) crude products purified by preparative HPLC;
(iv) isolation of the resulting peptides (details not speci-
fied). The compounds prepared were analyzed by HPLC,
but no details of melting points, CHN analyses, or mass
spectroscopic analyses of the final products were provid-
ed. The multiple reaction steps involved in the procedure,
the use of enzymes, and the preparative HPLC required
Treatment of N-(Cbz-a-pentapeptidoyl)benzotriazoles
12a and 12b with unprotected dipeptides 5c and 5d in
aqueous acetonitrile at 0 °C gave N-Cbz-heptapeptides
14a and 14b, respectively, in 79–82% yield; the products
were characterized by 1H and 13C NMR spectroscopic and
by elemental analyses (Scheme 7).
for purification suggests that the use of this procedure
would be difficult for the preparation of such peptides in
more than very small quantities. Our products 11a–d were
each characterized by 1H, 13C NMR spectroscopy and by
elemental analyses.
In conclusion, N-polypeptidoylbenzotriazoles are advan-
tageous coupling reagents that (i) are sufficiently reactive
to form amide bonds at ambient temperature; (ii) are sta-
ble enough to resist side reactions and can be stored in the
crystalline state at room temperature for at least five
months; (iii) provide good yields without detectable race-
mization; (iv) are almost always crystalline; (v) are rela-
tively insensitive to moisture and can be used in aqueous
solution, and (vi) are inexpensive to prepare. Hence, N-
We prepared N-(Cbz-a-pentapeptidoyl)benzotriazoles
12a and 12b in 78–85% yields by treatment of N-(Cbz-
pentapeptides) 8a and 8b with four equivalents of benzo-
triazole and one equivalent of thionyl chloride in either
tetrahydrofuran or acetonitrile at –30 °C (Scheme 5).
O
R2
O
R4
O
O
R2
O
R4
O
Bt-H
H
H
H
H
H
H
N
N
N
N
N
N
Cbz
N
N
OH
Cbz
N
N
Bt
SOCl2, THF
H
H
H
H
R1
O
R3
O
R5
R1
O
R3
O
R5
12a, 78%
12b, 85%
8a: R1 = Me, R2 = Bn, R3 = H, R4 = Me, R5 = Bn
8b: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me, R5 = Me
Scheme 5 N-(Cbz-a-pentapeptidoyl)benzotriazoles 12a and 12b (for details, see the experimental section)
O
O
O
O
O
O
O
OH
Et3N
H
H
H
H
H
H
N
N
N
N
N
N
OH
+
Cbz
N
N
Bt
Cbz
N
N
H
N
MeCN–H2O
H
H
H
H
H2N
O
O
O
O
O
12b
3j
13, 85%
Scheme 6 Preparation of N-Cbz-a-hexapeptide 13 from N-(Cbz-a-pentapeptidoyl)benzotriazole (12b) and L-Phe-OH (3j)
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

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Tri-, Tetra- and Pentapeptidoylbenzotriazoles
2999
R2
O
R4
O
R6
O
O
R2
O
R4
O
O
R6
O
HO
H
N
H
H
H
H
H
H
Et3N
N
N
N
N
N
N
O
Cbz
N
N
Bt
Cbz
N
N
N
OH
+
H
H
H
H
H
H2N
HN
MeCN–H2O
R1
O
R3
12a,b
O
R5
R1
O
R3
O
R5
O
R7
R7
5c, L-Ala-Gly
5d, Gly-Gly
14a,b
14a: R1 = Me, R2 = Bn, R3 = H, R4 = Me, R5 = Bn, R6 = Me, R7 = H, 82%
14b: R1 = Me, R2 = i-Bu, R3 = Me, R4 = Me, R5 = Me, R6 = H, R7 = H, 79%
Scheme 7 Preparation N-(Cbz-a-heptapeptides) 14a and 14b from N-(Cbz-a-pentapeptidoyl)benzotriazoles 12a and 12b and unprotected di-
peptides 5c and 5d
Table 4 General Comparison of Common Coupling Procedures with Solution-Phase Coupling using Tri-, Tetra-, and Pentapeptidoyl Benzo-
triazoles
Conventional
SPPS26–28
Automated
SPPS27,28
Microwave-assisted
SPPS29–31
Enzymatic peptide Solution-phase using
synthesis32,33
tri-, tetra- and penta-
peptidoyl benzotria-
zoles
Reagents used
Coupling time
PyBOP, PyBroP,
HOBt, DIC, DCC,
HATU, HBTU
PyBOP, PyBroP,
HOBt, DIC, DCC,
HATU, HBTU
PyBOP, PyBroP,
HOBt, DIC, DCC,
HATU, HBTU
PyBOP, DIC and as above
enzymes (trypsin,
a-chymotrypsin,
V8 protease)
45–360 min
60 min
3–16 equiv
yes
1.5–60 min
3–16 equiv
yes
960–7200 min
30–150 min
Reagent per substrate 3–10 equiv
Moisture-sensitive yes
Large-scale feasible no
5 equiv
yes
1 equiv
no
no
no
no
yes
Protection required for SH, OH and
indole NH
for SH, OH and
indole NH
for SH, OH and
indole NH
for SH, OH and
indole NH
not required except
for NH2
Yields
7–37
0–57
0–64
55–92
70–92
Purification
HPLC
HPLC
HPLC
RP-HPLC
recrystallization
filtrate was concentrated under reduced pressure. The residue was
diluted with EtOAc (100 mL) and the solution was washed with sat-
urated Na2CO3 (3 × 50 mL), brine (3 × 50 mL), and dried over
Na2SO4. Removal of the solvents under reduced pressure gave prod-
ucts 2a–f.
(Pg-a-tripeptidoyl)benzotriazoles, N-(Pg-a-tetrapeptid-
oyl)benzotriazoles, and N-(Pg-a-pentapeptidoyl)benzo-
triazole reagents allow efficient peptide couplings to
generate tetra-, penta-, hexa-, and heptapeptides in quan-
tity. A comparison of reagent stoichiometries and proto-
cols for some common SPPS coupling procedures with
the solution-phase coupling procedures using tri-, tetra-
and pentapeptidoyl benzotriazoles is given in Table 4.
Cbz-L-Ala-L-Phe-Gly-Bt (2a)
Yield: 80%; white microcrystals (CH2Cl2); mp 186.0–187.0 °C.
1H NMR (DMSO-d6): d = 8.81 (t, J = 5.6 Hz, 1 H), 8.30 (d,
J = 8.1 Hz, 1 H), 8.23 (d, J = 7.8 Hz, 1 H), 8.01 (d, J = 8.4 Hz, 1 H),
7.81 (t, J = 7.7 Hz, 1 H), 7.64 (t, J = 7.7 Hz, 1 H), 7.44 (d,
J = 8.1 Hz, 1 H), 7.35–7.15 (m, 10 H), 5.10–4.95 (m, 4 H), 4.75–
4.60 (m, 1 H), 4.10–4.00 (m, 1 H), 3.12 (dd, J = 13.8, 4.2 Hz, 1 H),
2.92 (dd, J = 13.8, 3.9 Hz, 1 H), 1.14 (d, J = 7.2 Hz, 3 H).
13C NMR (DMSO-d6): d = 172.2, 171.9, 168.4, 155.6, 145.2, 137.5,
136.9, 131.0, 130.5, 129.3, 128.3, 128.0, 127.7, 126.6, 126.2, 120.1,
113.7, 65.4, 53.5, 50.2, 42.6, 37.7, 18.1.
Melting points were determined with a MelTemp apparatus and are
1
uncorrected. H (300 MHz) and 13C (75 MHz) NMR spectra were
recorded with a Gemini 300 MHz spectrometer in DMSO-d6, unless
otherwise specified, with TMS as internal standard. The data are re-
ported as follows: chemical shift in parts per million (ppm, d units)
and spin–spin coupling (J, Hz). Mass spectra were obtained with a
Thermo-Finnigan LCQ spectrometer operating in the electrospray
ionization (ESI) mode. CH2Cl2 was dried and distilled over CaH2;
THF was used after distillation over Na/benzophenone.
Anal. Calcd for C28H28N6O5: C, 63.63; H, 5.34; N, 15.90. Found: C,
63.57; H, 5.295; N, 15.86.
Preparation of N-(Protected tripeptidoyl)benzotriazoles 2a–f;
General Procedure
Cbz-L-Phe-Gly-Gly-Bt (2b)
Yield: 80%; white microcrystals (CH2Cl2); mp 137.0–139.0 °C.
1H NMR (DMSO-d6): d = 8.59 (t, J = 5.3 Hz, 1 H), 8.44 (t,
J = 5.4 Hz, 1 H), 8.29 (d, J = 8.4 Hz, 1 H), 8.22 (d, J = 8.1 Hz, 1 H),
7.81 (t, J = 7.7 Hz, 1 H), 7.68–7.48 (m, 2 H), 7.40–7.20 (m, 10 H),
5.10–5.00 (m, 2 H), 4.94 (s, 2 H), 4.40–4.28 (m, 1 H), 3.92 (d,
Thionyl chloride (5 mmol) was added to a solution of 1H-benzotri-
azole (20 mmol) in anhydrous THF (15 mL) at 20 °C, and stirred for
20 min. The reaction mixture was cooled to –45 °C, then N-protect-
ed tripeptide 1a–f (5 mmol), dissolved in anhydrous THF (5 mL),
was added dropwise, and the mixture was stirred for 4 h. The white
precipitate that formed during the reaction was filtered off, and the
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

3000
A. Abdelmajeid et al.
PAPER
J = 6.0 Hz, 2 H), 3.08 (dd, J = 13.8, 3.6 Hz, 1 H), 2.85–2.70 (m,
1 H).
13C NMR (DMSO-d6): d = 171.9, 169.7, 168.5, 155.9, 145.2, 138.1,
136.9, 131.0, 130.5, 129.2, 128.2, 128.0, 127.6, 127.4, 126.6, 126.2,
120.1, 113.7, 65.2, 56.2, 42.5, 41.8, 37.4.
13C NMR (DMSO-d6): d = 172.4, 171.8, 171.4, 155.8, 145.3, 137.0,
131.1, 130.6, 128.3, 127.6, 126.7, 120.2, 113.9, 65.3, 51.2, 50.1,
48.7, 32.2, 29.3, 18.0, 16.5, 14.7.
Anal. Calcd for C25H30N6O5S: C, 57.02; H, 5.74; N, 15.96. Found:
C, 56.63; H, 5.76; N, 15.67.
Anal. Calcd for C27H26N6O5: C, 63.03; H, 5.09; N, 16.33. Found: C,
62.76; H, 5.02; N, 16.25.
Preparation of Tetrapeptides 4a–l and Pentapeptides 6a–c;
General Procedure
N-(Protected tripeptidoyl)benzotriazoles 2a–f (0.2 mmol) were
added at 0 °C to a solution of a-amino acid 3a–i and/or dipeptide 5a
or 5b (0.2 mmol) in a mixture of MeCN (7 mL) and H2O (3 mL) in
the presence of Et3N (0.24 mmol). The reaction mixture was then
stirred at 0 °C until the starting material was completely consumed
(40–100 min for tetrapeptides and 100–150 min for pentapeptides).
After 4 M HCl (1 mL) was added, the solution was concentrated un-
der reduced pressure. The residue was extracted with EtOAc (20
mL), washed with 4 M HCl (3 × 10 mL) and brine (3 × 10 mL), and
then dried over anhydrous (Na2SO4). Evaporation of the solvent
gave the desired products 4a–l and 6a–c in pure forms.
Cbz-L-Phe-L-Ala-L-Ala-Bt (2c)
Yield: 73%; white microcrystals (CH2Cl2); mp 190.0–192.0 °C.
1H NMR (DMSO-d6): d = 8.83 (d, J = 5.7 Hz, 1 H), 8.29 (d,
J = 8.1 Hz, 1 H), 8.23 (dd, J = 13.2, 8.4 Hz, 2 H), 7.80 (t,
J = 7.7 Hz, 1 H), 7.64 (t, J = 7.7 Hz, 1 H), 7.49 (d, J = 8.7 Hz, 1 H),
7.35–7.15 (m, 10 H), 5.65–5.55 (m, 1 H), 4.92 (s, 2 H), 4.45–4.35
(m, 1 H), 4.30–4.20 (m, 1 H), 2.99 (dd, J = 10.8, 3.8 Hz, 1 H), 2.75–
2.60 (m, 1 H), 1.57 (d, J = 7.2 Hz, 3 H), 1.28 (d, J = 6.9 Hz, 3 H).
13C NMR (DMSO-d6): d = 172.5, 171.8, 171.2, 155.8, 145.3, 138.1,
137.0, 131.1, 129.2, 128.2, 128.0, 127.6, 127.3, 126.7, 126.2, 125.3,
120.2, 113.9, 65.1, 56.0, 48.6, 47.6, 37.4, 18.2, 16.6.
Cbz-L-Ala-L-Phe-Gly-L-Ile-OH (4a)
Yield: 75%; white microcrystals; mp 90.0–92.0 °C.
Anal. Calcd for C29H30N6O5·H2O: C, 62.13; H, 5.39; N, 14.99.
Found: C, 62.11; H, 5.27; N, 14.56.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.30–8.20 (m, 1 H),
7.99–7.85 (m,2 H), 7.41 (d, J = 7.5 Hz, 1 H), 7.36–7.30 (br s, 5 H),
7.25–7.15 (m, 5 H), 5.00 (br s, 2 H), 4.52–4.45 (m, 1 H), 4.22 (dd,
J = 8.4, 6.0 Hz, 1 H), 4.05–3.95 (m, 1 H), 3.80–3.75 (m, 2 H), 3.10–
2.90 (m, 1 H), 2.85 (dd, J = 20.4, 13.5 Hz, 1 H), 1.85–1.75 (m, 1 H),
1.45–1.30 (m, 1 H), 1.25–1.08 (m, 4 H), 0.90–0.70 (m, 6 H).
13C NMR (DMSO-d6): d = 172.8, 172.3, 171.1, 168.6, 155.6, 142.9,
137.7, 136.9, 129.3, 128.3, 128.0, 127.8, 126.2, 65.5, 56.2, 53.8,
50.2, 41.8, 37.5, 36.5, 24.7, 18.1, 15.6, 11.3.
Fmoc-L-Phe-L-Ala-L-Val-Bt (2d)
Yield: 76%; white microcrystals (CH2Cl2); mp 162.0–164.0 °C.
1H NMR (DMSO-d6): d = 8.59 (d, J = 6.3 Hz, 1 H), 8.35–8.20 (m,
2 H), 7.87 (d, J = 7.2 Hz, 1 H), 7.84–7.75 (m, 1 H), 7.70–7.54 (m,
4 H), 7.43–7.35 (m, 2 H), 7.34–7.20 (m, 6 H), 7.18 (d, J = 6.9 Hz,
1 H), 5.60 (t, J = 6.0 Hz, 1 H), 4.51–4.45 (m, 1 H), 4.30–4.20 (m,
1 H), 4.15–4.10 (m, 3 H), 3.05–2.95 (m, 1 H), 2.80–2.70 (m, 1 H),
2.45–2.30 (m, 1 H), 1.26 (d, J = 6.6 Hz, 3 H), 1.10–0.95 (m, 6 H).
13C NMR (DMSO-d6): d = 173.0, 171.3, 171.1, 155.8, 145.3, 143.7,
140.6, 138.2, 131.1, 130.4, 129.2, 128.0, 127.6, 127.0, 126.8, 126.2,
125.3, 120.2, 120.0, 113.9, 65.7, 57.6, 56.0, 47.8, 46.5, 37.4, 30.1,
19.3, 18.1, 17.9.
Anal. Calcd for C28H36N4O7: C, 62.21; H, 6.71; N, 10.36. Found: C,
62.01; H, 6.79; N, 10.46.
Cbz-L-Ala-L-Phe-Gly-L-Ala-OH (4b)
Yield: 86%; white microcrystals (CH2Cl2–hexanes); mp 172.0–
174.0 °C.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.26 (t, J = 5.6 Hz,
1 H), 8.08 (d, J = 6.9 Hz, 1 H), 7.98 (d, J = 7.8 Hz, 1 H), 7.41 (d,
J = 7.5 Hz, 1 H), 7.35–7.30 (m, 5 H), 7.25–7.15 (m, 5 H), 5.10–
4.90 (m, 2 H), 4.50–4.45 (m, 1 H), 4.30–4.15 (m, 1 H), 4.10–3.95
(m, 1 H), 3.71 (d, J = 5.7 Hz, 2 H), 3.05 (dd, J = 14.1, 4.5 Hz, 1 H),
2.81 (dd, J = 13.8, 9.3 Hz, 1 H), 1.28 (d, J = 7.2 Hz, 3 H), 1.12 (d,
J = 7.2 Hz, 3 H).
Anal. Calcd for C38H38N6O5: C, 69.28; H, 5.81; N, 12.76. Found: C,
69.16; H, 5.90; N, 12.75.
Cbz-L-Ala-L-Leu-L-Ala-Bt (2e)
Yield: 86%; white microcrystals (CH2Cl2–hexanes); mp 175.0–
176.0 °C.
1H NMR (DMSO-d6): d = 8.82 (d, J = 6.3 Hz, 1 H), 8.29 (d,
J = 6.3 Hz, 1 H), 8.22 (d, J = 6.3 Hz, 1 H), 7.87 (d, J = 7.2 Hz, 1 H),
7.80 (t, J = 6.0 Hz, 1 H), 7.64 (t, J = 6.0 Hz, 1 H), 7.50–7.40 (m,
1 H), 7.38–7.25 (m, 5 H), 5.60–5.50 (m, 1 H), 5.01 (s, 2 H), 4.48–
4.40 (m, 1 H), 4.10–4.00 (m, 1 H), 1.70–1.60 (m, 1 H), 1.56 (d,
J = 6.6 Hz, 3 H), 1.50–1.45 (m, 2 H), 1.17 (d, J = 6.6 Hz, 3 H),
0.95–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 172.4, 172.2, 171.7, 155.6, 145.3, 137.0,
131.0, 130.6, 128.3, 127.6, 126.6, 120.1, 113.9, 65.3, 50.2, 50.1,
48.6, 41.0, 24.1, 23.1, 21.6, 18.1, 16.5.
13C NMR (DMSO-d6): d = 173.9, 172.4, 171.1, 168.3, 155.6, 137.6,
136.9, 129.2, 128.3, 128.0, 127.8, 126.2, 65.5, 53.9, 50.2, 47.5,
41.7, 37.4, 18.1, 17.3.
Anal. Calcd for C25H30N4O7: C, 60.23; H, 6.07; N, 11.24. Found: C,
60.34; H, 6.20; N, 11.17.
Cbz-L-Phe-Gly-Gly-L-Trp-OH (4c)
Yield: 80%; white microcrystals (CH2Cl2); mp 141.0–143.0 °C.
Anal. Calcd for C26H32N6O5: C, 61.40; H, 6.34; N, 16.52. Found: C,
61.49; H, 6.51; N, 16.10.
1H NMR (DMSO-d6): d = 12.75 (br s, 1 H), 10.86 (s, 1 H), 8.45–
8.30 (m, 1 H), 8.15 (d, J = 7.2 Hz, 1 H), 8.10–8.05 (m, 1 H), 7.60–
7.50 (m, 2 H), 7.40–7.10 (m, 13 H), 7.06 (t, J = 7.7 Hz, 1 H), 7.00
(t, J = 7.2 Hz, 1 H), 4.93 (br s, 2 H), 4.55–4.45 (m, 1 H), 4.35–4.20
(m, 1 H), 3.90–3.60 (m, 4 H), 3.17 (dd, J = 14.1, 5.2 Hz, 1 H), 3.10–
3.00 (m, 2 H), 2.80–2.65 (m, 1 H).
13C NMR (DMSO-d6): d = 173.1, 171.9, 168.8, 168.5, 155.9, 138.1,
136.9, 136.0, 129.2, 128.2, 128.0, 127.6, 127.4, 127.2, 126.2, 123.7,
120.9, 118.3, 118.1, 111.3, 109.6, 65.2, 56.1, 53.0, 42.1, 41.7, 37.4,
27.1.
Cbz-L-Ala-L-Met-L-Ala-Bt (2f)
Yield: 81%; white microcrystals (CH2Cl2); mp 188.0–189.0 °C.
1H NMR (DMSO-d6): d = 8.86 (d, J = 5.4 Hz, 1 H), 8.30 (d,
J = 8.1 Hz, 1 H), 8.23 (d, J = 8.1 Hz, 1 H), 7.99 (d, J = 7.8 Hz,
1 H), 7.81 (t, J = 7.2 Hz, 1 H), 7.64 (t, J = 7.7 Hz, 1 H), 7.48 (d,
J = 7.5 Hz, 1 H), 7.38–7.25 (m, 5 H), 5.65–5.55 (m, 1 H), 5.00 (s,
2 H), 4.50–4.40 (m, 1 H), 4.10–4.00 (m, 1 H), 2.49–2.40 (m, 2 H),
2.05 (s, 3 H), 1.95–1.80 (m, 2 H), 1.57 (d, J = 7.2 Hz, 3 H), 1.17 (d,
J = 6.9 Hz, 3 H).
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

PAPER
Tri-, Tetra- and Pentapeptidoylbenzotriazoles
3001
Anal. Calcd for C32H33N5O7·H2O: C, 62.23; H, 5.71; N, 11.34.
Found: C, 62.25; H, 5.96; N, 9.56.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.35–8.20 (m, 2 H),
7.87 (d, J = 7.2 Hz, 2 H), 7.79 (d, J = 8.4 Hz, 1 H), 7.62 (t,
J = 7.4 Hz, 2 H), 7.40 (t, J = 7.1 Hz, 2 H), 7.35–7.20 (m, 7 H),
7.19–7.12 (m, 1 H), 4.45–4.16 (m, 5 H), 4.15–4.00 (m, 2 H), 3.05–
2.95 (m, 1 H), 2.80–2.74 (m, 1 H), 2.48–2.40 (m, 2 H), 2.05–1.80
(m, 6 H), 1.30–1.20 (m, 3 H), 0.90–0.70 (m, 6 H).
Cbz-L-Phe-Gly-Gly-L-Val-OH (4d)
Yield: 83%; white microcrystals (CH2Cl2–hexanes); mp 96.0–
98.0 °C.
1H NMR (DMSO-d6): d = 8.38–8.30 (m, 1 H), 8.06–7.90 (m, 2 H),
7.55 (d, J = 8.4 Hz, 1 H), 7.35–7.18 (m, 10 H), 5.00–4.90 (m, 2 H),
4.35–4.30 (m, 1 H), 4.17 (dd, J = 8.4, 6.0 Hz, 1 H), 4.05–3.75 (m,
4 H), 3.06 (dd, J = 13.8, 3.9 Hz, 1 H), 2.80–2.70 (m, 1 H), 2.10–
2.05 (m, 1 H), 0.88 (d, J = 6.9 Hz, 6 H).
13C NMR (DMSO-d6): d = 172.9, 172.0, 169.0, 168.9, 156.0, 138.2,
137.0, 129.3, 128.3, 128.1, 127.7, 127.5, 126.3, 65.3, 57.2, 56.2,
42.1, 41.7, 37.4, 29.9, 19.2, 18.0.
13C NMR (DMSO-d6): d = 173.0, 171.9, 171.3, 170.9, 155.7, 143.7,
140.6, 138.2, 129.2, 127.9, 127.6, 127.0, 126.2, 125.2, 120.0, 65.6,
57.4, 56.0, 50.8, 48.2, 46.5, 37.4, 30.8, 30.6, 29.6, 19.1, 18.0, 14.6.
HRMS (ESI+): m/z [M + H]+ calcd for C37H44N4O7S: 689.3003;
found: 689.3005; m/z [M + Na]+ calcd for C37H44N4O7SNa:
711.2823; found: 711.2854; m/z [M – H + 2Na]+ calcd for
C37H43N4O7SNa2: 733.2642; found: 733.2676.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-OH (4i)
Yield: 88%; white microcrystals (EtOH); mp 232.0–234.0 °C.
Anal. Calcd for C26H32N4O7·H2O: C, 58.86; H, 6.46; N, 10.56.
Found: C, 58.78; H, 6.16; N, 10.14.
1H NMR (DMSO-d6): d = 12.50 (br s, 1 H), 8.09 (d, J = 6.9 Hz,
1 H), 7.95–7.85 (m, 2 H), 7.46 (d, J = 7.5 Hz, 1 H), 7.38–7.28 (m,
5 H), 5.01 (s, 2 H), 4.35–4.22 (m, 2 H), 4.20–4.12 (m, 1 H), 4.10–
4.00 (m, 1 H), 1.65–1.55 (m, 1 H), 1.50–1.40 (m, 2 H), 1.26 (d,
J = 7.2 Hz, 3 H), 1.20 (d, J = 7.2 Hz, 6 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 173.9, 172.4, 171.7, 171.5, 155.6, 137.0,
128.3, 127.7, 65.4, 50.9, 50.1, 47.7, 47.4, 40.8, 24.1, 23.1, 21.6,
18.2, 17.2.
Cbz-L-Phe-L-Ala-L-Ala-L-Met-OH (4e)
Yield: 76%; white microcrystals (CH2Cl2); mp 182.0–184.0 °C.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.19 (d, J = 7.2 Hz,
1 H), 8.12 (d, J = 7.8 Hz, 1 H), 8.00 (d, J = 7.5 Hz, 1 H), 7.52 (d,
J = 8.1 Hz, 1 H), 7.35–7.20 (m, 10 H), 4.94 (s, 2 H), 4.40–4.20 (m,
4 H), 3.40–3.35 (m, 2 H), 3.05–2.95 (m, 1 H), 2.80–2.65 (m, 1 H),
2.00 (s, 3 H), 2.00–1.95 (m, 1 H), 1.89–1.80 (m, 1 H), 1.25–1.20
(m, 6 H).
13C NMR (DMSO-d6): d = 173.1, 172.2, 171.7, 171.3, 155.9, 138.2,
137.0, 129.2, 128.3, 128.0, 127.6, 127.4, 126.8, 126.2, 65.2, 56.1,
50.8, 48.1, 47.9, 37.4, 30.8, 29.6, 18.2, 14.6.
Anal. Calcd for C23H34N4O7: C, 57.73; H, 7.16; N, 11.71. Found: C,
57.42; H, 7.24; N, 11.44.
Cbz-L-Ala-L-Leu-L-Ala-DL-Ala-OH (4i+4i¢)
Yield: 85%; white microcrystals (CH2Cl2); mp 226.0–228.0 °C.
Anal. Calcd for C28H36N4O7S: C, 58.72; H, 6.34; N, 9.78. Found: C,
58.45; H, 6.71; N, 9.70.
1H NMR (DMSO-d6): d = 8.07 (d, J = 7.2 Hz, 1 H), 7.90 (d,
J = 7.5 Hz, 2 H), 7.45 (d, J = 7.2 Hz, 1 H), 7.38–7.26 (m, 5 H), 5.01
(s, 2 H), 4.30–4.21 (m, 2 H), 4.20–4.12 (m, 1 H), 4.10–4.00 (m,
1 H), 1.65–1.55 (m, 1 H), 1.50–1.40 (m, 2 H), 1.25 (d, J = 7.2 Hz,
3 H), 1.19 (d, J = 7.2 Hz, 6 H), 0.90–0.50 (m, 6 H).
Cbz-L-Phe-L-Ala-L-Ala-L-Asp-OH (4f)
Yield: 70%; white microcrystals (CH2Cl2–hexanes); mp 173.0–
175.0 °C.
1H NMR (DMSO-d6): d = 8.28–8.15 (m, 1 H), 8.13 (d, J = 7.8 Hz,
1 H), 8.08–8.00 (m, 1 H), 7.54–7.45 (m, 1 H), 7.38–7.15 (m, 10 H),
4.93 (s, 2 H), 4.55–4.48 (m, 1 H), 4.35–4.20 (m, 3 H), 3.10–2.90
(m, 1 H), 2.75–2.68 (m, 1 H), 2.67–2.55 (m, 2 H), 1.30–1.15 (m,
6 H).
13C NMR (DMSO-d6): d = 172.2, 171.8, 171.6, 171.2, 155.8, 138.1,
137.0, 129.2, 128.2, 128.0, 1 27.6, 127.3, 126.2, 65.1, 56.0, 48.5,
48.0, 47.8, 37.4, 35.9, 18.2.
13C NMR (DMSO-d6): d = 173.9, 172.4, 171.7, 171.5, 155.6, 137.0,
128.3, 127.7, 65.4, 50.9, 50.1, 47.7, 47.5, 40.8, 24.1, 23.1, 21.6,
18.2, 17.2.
Anal. Calcd for C23H34N4O7: C, 57.73; H, 7.16; N, 11.71. Found: C,
57.57; H, 7.36; N, 11.60.
Cbz-L-Ala-L-Met-L-Ala-L-Ala-OH (4j)
Yield: 92%; white microcrystals (MeOH); mp 242.0–244.0 °C.
Anal. Calcd for C27H32N4O·H2O: C, 56.44; H, 5.96; N, 9.75. Found:
C, 55.79; H, 5.82; N, 9.40.
1H NMR (DMSO-d6): d = 12.53 (br s, 1 H), 8.14 (d, J = 6.9 Hz,
1 H), 8.05–7.93 (m, 2 H), 7.50 (d, J = 7.2 Hz, 1 H), 7.38–7.30 (m,
5 H), 5.01 (s, 2 H), 4.38–4.24 (m, 2 H), 4.23–4.18 (m, 1 H), 4.10–
4.00 (m, 1 H), 2.48–2.40 (m, 2 H), 2.02 (s, 3 H), 1.95–1.75 (m,
2 H), 1.26 (d, J = 7.2 Hz, 3 H), 1.23–1.18 (m, 6 H).
Fmoc-L-Phe-L-Ala-L-Val-L-Leu-OH (4g)
Yield: 90%; white microcrystals (CH2Cl2); mp 223.0–225.0 °C.
1H NMR (DMSO-d6): d = 12.50 (br s, 1 H), 8.26 (d, J = 6.6 Hz,
1 H), 8.15 (d, J = 7.8 Hz, 1 H), 7.87 (d, J = 7.2 Hz, 2 H), 7.75 (d,
J = 9.0 Hz, 1 H), 7.62 (t, J = 7.05 Hz, 2 H), 7.40 (t, J = 7.4 Hz,
2 H), 7.35–7.23 (m, 5 H), 7.22–7.15 (m, 2 H), 4.45–4.30 (m, 1 H),
4.25–4.20 (m, 2 H), 4.18–4.00 (m, 3 H), 3.10–2.95 (m, 1 H), 2.80–
2.70 (m, 1 H), 2.10–1.90 (m, 1 H), 1.70–1.65 (m, 1 H), 1.60–1.45
(m, 2 H), 1.30–1.20 (m, 3 H), 0.95–0.70 (m, 12 H).
13C NMR (DMSO-d6): d = 173.8, 171.9, 171.3, 170.8, 155.8, 143.7,
140.6, 138.2, 129.2, 128.0, 127.6, 127.0, 126.2, 125.3, 120.0, 65.7,
57.3, 56.0, 50.1, 48.2, 46.6, 37.5, 30.9, 24.3, 22.9, 21.3, 19.2, 18.0.
13C NMR (DMSO-d6): d = 174.0, 172.5, 171.8, 170.5, 155.7, 137.0,
128.4, 127.7, 65.4, 51.7, 50.1, 47.9, 47.5, 32.1, 29.4, 18.2, 18.0,
17.2, 14.7.
Anal. Calcd for C22H32N4O7S: C, 53.21; H, 6.50; N, 11.28. Found:
C, 53.19; H, 6.61; N, 11.08.
Cbz-L-Ala-L-Phe-Gly-L-Cys-OH (4k)
Yield: 82%; white microcrystals (CH2Cl2); mp 165.0–167.0 °C.
1H NMR (DMSO-d6): d = 8.35–8.28 (m, 1 H), 8.11 (d, J = 7.8 Hz,
1 H), 7.98 (d, J = 7.8 Hz, 1 H), 7.41 (d, J = 7.8 Hz, 1 H), 7.36–7.30
(m, 5 H), 7.25–7.20 (m, 5 H), 5.00 (s, 2 H), 4.55–4.40 (m, 2 H),
4.05–3.95 (m, 1 H), 3.80 (d, J = 4.2 Hz, 2 H), 3.10–3.00 (m, 2 H),
2.90–2.75 (m, 2 H), 1.12 (d, J = 6.9 Hz, 3 H).
Anal. Calcd for C38H46N4O7: C, 68.04; H, 6.91; N, 8.35. Found: C,
67.79; H, 7.12; N, 8.21.
Fmoc-L-Phe-L-Ala-L-Val-L-Met-OH (4h)
Yield: 88%; white microcrystals (CH2Cl2); mp 196.0–198.0 °C.
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

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A. Abdelmajeid et al.
PAPER
13C NMR (DMSO-d6): d = 172.4, 171.4, 168.7, 155.6, 137.6, 136.9,
129.2, 128.3, 128.0, 127.8, 126.2, 65.5, 54.3, 53.9, 50.2, 45.5, 41.9,
37.4, 25.7, 18.1.
ture was stirred for 30 min. The reaction mixture was cooled to
–20 °C, then N-protected tetrapeptides 2b, 2g, 2i, or 2j (5 mmol),
dissolved in anhydrous THF (5 mL), were added dropwise, and the
mixture was stirred for 4 h. The white precipitate that formed during
the reaction was filtered off, and the filtrate was concentrated under
reduced pressure. The residue was diluted with EtOAc (100 mL)
and the solution was washed with saturated Na2CO3 (3 × 30 mL),
and dried over anhydrous Na2SO4. Removal of the solvent under re-
duced pressure gave the desired products 7a–d.
Anal. Calcd for C25H30N4O7S: C, 56.59; H, 5.70; N, 10.56. Found:
C, 56.48; H, 5.89; N, 10.46.
Cbz-L-Phe-L-Gly-L-Gly-L-Ser-OH (4l)
Yield: 72%; white microcrystals (CH2Cl2–hexanes); mp 65.0–
67.0 °C.
1H NMR (DMSO-d6): d = 7.70–7.60 (m,1 H), 7.40–7.00 (m, 12 H),
6.00–5.80 (m, 1 H), 5.00–4.90 (m, 2 H), 4.88–4.80 (m, 1 H), 4.52–
4.40 (m, 1 H), 4.05–3.70 (m, 6 H), 3.15–3.00 (m, 1 H), 2.90–2.80
(m, 1 H).
13C NMR (DMSO-d6): d = 173.2, 170.9, 156.9, 136.7, 136.2, 129.4,
128.6, 128.2, 127.9, 127.0, 67.2, 56.6, 42.9, 41.5, 38.2, 29.9.
Cbz-L-Ala-L-Phe-Gly-L-Ala-Bt (7a)
Yield: 75%; white microcrystals (CH2Cl2–hexanes); mp 212.0–
214.0 °C.
1H NMR (DMSO-d6): d = 8.71 (d, J = 5.4 Hz, 1 H), 8.35–8.25 (m,
2 H), 8.22 (d, J = 6.9 Hz, 1 H), 8.00 (d, J = 7.5 Hz, 1 H), 7.81 (t,
J = 7.7 Hz, 1 H), 7.65 (t, J = 7.7 Hz, 1 H), 7.43 (d, J = 6.6 Hz, 1 H),
7.35–7.30 (m, 5 H), 7.25–7.18 (m, 5 H), 5.70–5.60 (m, 1 H), 5.10–
4.95 (m, 2 H), 4.55–4.40 (m, 1 H), 4.05–3.95 (m, 1 H), 3.82 (d,
J = 5.1 Hz, 2 H), 3.05–2.95 (m, 1 H), 2.90–2.75 (m, 1 H), 1.57 (d,
J = 6.0 Hz, 3 H), 1.11 (d, J = 7.2 Hz, 3 H).
Anal. Calcd for C24H28N4O8: C, 57.59; H, 5.64; N, 11.19. Found: C,
57.26; H, 5.75; N, 11.34.
Cbz-L-Ala-L-Phe-Gly-Gly-L-Ala-OH (6a)
13C NMR (DMSO-d6): d = 172.5, 171.8, 171.2, 169.1, 155.6, 145.3,
137.6, 136.9, 131.1, 130.6, 129.2, 128.3, 128.0, 127.7, 126.7, 126.2,
120.2, 113.9, 65.5, 54.0, 50.2, 48.5, 41.5, 37.3, 18.0, 16.8.
Yield: 73%; white microcrystals (CH2Cl2); mp 154.0–156.0 °C.
1H NMR (DMSO-d6): d = 12.59 (br s, 1 H), 8.38–8.35 (m, 1 H), 8.2
(d, J = 6.9 Hz, 1 H), 8.08–8.00 (m, 1 H), 8.00–7.90 (m, 1 H), 7.38–
7.25 (m, 6 H), 7.24–7.20 (m, 5 H), 5.00 (br s, 2 H), 4.60–4.50 (m,
1 H), 4.05–3.95 (m, 1 H), 3.85–3.65 (m, 4 H), 3.10–3.00 (m, 1 H),
2.90–2.75 (m, 1 H), 1.27 (d, J = 7.2 Hz, 2 H), 1.11 (d, J = 6.9 Hz,
5 H).
13C NMR (DMSO-d6): d = 173.9, 172.3, 171.3, 168.8, 168.3, 155.6,
137.6, 136.9, 129.2, 128.3, 127.9, 127.7, 126.2, 65.4, 53.7, 50.2,
47.4, 42.1, 41.6, 37.6, 18.1, 17.2.
Anal. Calcd for C31H33N7O6: C, 62.09; H, 5.55; N, 16.35. Found: C,
62.06; H, 5.71; N, 15.32.
Fmoc-L-Phe-L-Ala-L-Val-L-Leu-Bt (7b)
Yield: 78%; white microcrystals (CH2Cl2–hexanes); mp 206.0–
208.0 °C.
1H NMR (DMSO-d6): d = 8.85–8.75 (m, 1 H), 8.35–8.18 (m, 3 H),
7.87 (d, J = 6.9 Hz, 2 H), 7.85–7.74 (m, 2 H), 7.70–7.55 (m, 4 H),
7.45–7.35 (m, 2 H), 7.33–7.15 (m, 7 H), 5.70–5.60 (m, 1 H), 4.45–
4.38 (m, 1 H), 4.35–4.30 (m, 1 H), 4.20–4.00 (m, 3 H), 3.10–2.95
(m, 1 H), 2.73 (dd, J = 18.9, 11.4 Hz, 1 H), 2.10–1.90 (m, 1 H),
1.85–1.65 (m, 2 H), 1.25–1.15 (m, 3 H), 1.12–1.05 (m, 2 H), 0.98–
0.79 (m, 12 H).
13C NMR (DMSO-d6): d = 172.0, 171.8, 171.5, 171.3, 155.8, 145.3,
143.7, 140.6, 138.2, 131.0, 130.5, 129.2, 128.0, 127.6, 127.0, 126.7,
126.2, 125.3, 120.0, 114.0, 65.6, 64.9, 57.1, 56.0, 51.2, 48.2, 46.5,
37.4, 30.8, 24.7, 23.0, 21.0, 19.1, 18.0, 15.2.
Anal. Calcd for C27H33N5O8·H2O: C, 56.54; H, 5.80; N, 12.21.
Found: C, 56.46; H, 5.67; N, 10.71.
Cbz-L-Phe-Gly-Gly-Gly-L-Leu-OH (6b)
Yield: 79%; white microcrystals (CH2Cl2); mp 202.0–204.0 °C.
1H NMR (DMSO-d6): d = 12.59 (s, 1 H), 8.36–8.10 (m, 1 H), 8.14–
8.00 (m, 3 H), 7.58 (d, J = 8.1 Hz, 1 H), 7.40–7.20 (m, 10 H), 4.94
(s, 1 H), 4.40–4.15 (m, 2 H), 3.85–3.65 (m, 6 H), 3.10–3.00 (m,
1 H), 2.80–2.70 (m, 1 H), 1.70–1.58 (m, 1 H), 1.55–1.45 (m, 2 H),
0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 173.9, 171.9, 169.1, 168.9, 168.6, 155.9,
138.2, 137.0, 129.2, 128.3, 128.0, 127.7, 127.4, 126.2, 65.3, 56.2,
50.2, 42.2, 41.6, 37.4, 24.3, 22.9, 21.4.
Anal. Calcd for C44H49N7O6: C, 68.46; H, 6.40; N, 12.70. Found: C,
68.07; H, 6.77; N, 12.59.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-Bt (7c)
Yield: 84%; white microcrystals (CHCl3–hexanes); mp 205.0–
206.0 °C.
Anal. Calcd for C29H37N5O8·H2O: C, 57.89; H, 6.53; N, 11.64.
Found: C, 57.59; H, 6.37; N, 11.30.
1H NMR (DMSO-d6): d = 8.74 (d, J = 5.7 Hz, 1 H), 8.29 (d,
J = 8.1 Hz, 1 H), 8.22 (d, J = 7.8 Hz, 1 H), 7.95 (d, J = 7.5 Hz, 1 H),
7.87 (d, J = 8.1 Hz, 1 H), 7.80 (t, J = 7.1 Hz, 1 H), 7.64 (t,
J = 7.2 Hz, 1 H), 7.45 (d, J = 7.2 Hz, 1 H), 7.38–7.30 (m, 5 H),
5.60–5.50 (m, 1 H), 5.01 (s, 2 H), 4.38–4.22 (m, 2 H), 4.10–4.00
(m, 1 H), 1.55 (d, J = 7.2 Hz, 4 H), 1.45–1.35 (m, 2 H), 1.25 (d,
J = 6.9 Hz, 3 H), 1.18 (d, J = 7.2 Hz, 3 H), 0.95–0.75 (m, 6 H).
13C NMR (DMSO-d6): d = 172.4, 172.3, 171.7, 171.5, 155.6, 145.3,
137.0, 131.0, 130.6, 128.3, 127.7, 126.7, 120.2, 113.9, 65.3, 50.7,
50.1, 48.5, 47.5, 40.8, 24.1, 23.1, 21.5, 18.1, 16.6.
Cbz-L-Phe-L-Ala-L-Ala-Gly-L-Leu-OH (6c)
Yield: 81%; white microcrystals (CH2Cl2); mp 198.0–200.0 °C.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.25–7.85 (m, 4 H),
7.55–7.45 (m, 1 H), 7.30–7.10 (m, 10 H), 4.94 (br s, 2 H), 4.40–
4.15 (m, 4 H), 3.80–3.70 (m, 2 H), 3.10–2.95 (m, 1 H), 2.80–2.70
(m, 1 H), 1.65–1.58 (m, 1 H), 1.55–1.45 (m, 2 H), 1.25–1.20 (m,
6 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 173.9, 172.3, 171.8, 171.3, 168.6, 155.9,
138.2, 137.0, 129.2, 128.3, 128.0, 127.7, 127.4, 126.2, 65.2, 56.1,
50.2, 48.3, 41.7, 37.4, 24.2, 22.9, 21.4, 18.1, 15.2.
Anal. Calcd for C29H37N7O6: C, 60.09; H, 6.43; N, 16.91. Found: C,
60.07; H, 6.62; N, 16.46.
Anal. Calcd for C31H41N5O8: C, 60.87; H, 6.76; N, 11.45. Found: C,
60.78; H, 6.76; N, 11.09.
Cbz-L-Ala-L-Met-L-Ala-L-Ala-Bt (7d)
Yield: 86%; white microcrystals (CH2Cl2–hexanes); mp 183.0–
185.0 °C.
Preparation of N-(Protected tetrapeptidoyl)benzotriazoles
7a–d; General Procedure
Thionyl chloride (5 mmol) was added to a solution of 1H-benzotri-
azole (20 mmol) in anhydrous THF (15 mL) at 20 °C, and the mix-
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

PAPER
Tri-, Tetra- and Pentapeptidoylbenzotriazoles
3003
1H NMR (DMSO-d6): d = 8.78 (d, J = 5.4 Hz, 1 H), 8.30 (d,
J = 8.4 Hz, 1 H), 8.22 (d, J = 8.1 Hz, 1 H), 8.05–7.93 (m, 2 H), 7.80
(t, J = 7.4 Hz, 1 H), 7.64 (t, J = 7.7 Hz, 1 H), 7.49 (d, J = 6.9 Hz,
1 H), 7.40–7.30 (m, 5 H), 5.60–5.20 (m, 1 H), 5.01 (s, 2 H), 4.39–
4.28 (m, 2 H), 4.10–4.02 (m, 1 H), 2.45–2.40 (m, 2 H), 1.98 (s,
3 H), 1.94–1.70 (m, 2 H), 1.56 (d, J = 7.2 Hz, 3 H), 1.30–1.22 (m,
3 H), 1.19 (d, J = 6.9 Hz, 3 H).
13C NMR (DMSO-d6): d = 172.5, 171.7, 170.5, 155.7, 145.3, 136.9,
131.1, 130.6, 128.3, 127.7, 126.7, 120.2, 113.9, 65.3, 51.6, 50.1,
48.5, 47.6, 32.1, 29.4, 18.0, 16.9, 16.6, 14.6.
13C NMR (DMSO-d6): d = 172.4, 171.8, 171.4, 168.4, 166.2, 155.9,
146.0, 140.5, 138.2, 137.0, 129.3, 129.0, 128.3, 128.0, 127.7, 127.4,
127.0, 126.2, 125.0, 119.9, 65.2, 56.2, 53.1, 51.4, 48.4, 46.5, 42.0,
41.2, 37.4, 35.9, 34.4, 24.1, 23.2, 21.6, 18.2.
HRMS (ESI+): m/z [M + Na]+ calcd for C48H56N6O9SNa: 915.3722;
found: 915.3764; m/z [M – H + 2Na]+ calcd for C48H55N6O9SNa2:
937.3541; found: 937.3579.
Cbz-L-Ala-L-Phe-Gly-L-Ala-Gly-L-Leu-OH (11a)
Yield: 80%; white microcrystals (MeOH); mp 152.0–154.0 °C.
Anal. Calcd for C28H35N7O6S: C, 56.27; H, 5.90; N, 16.40. Found:
C, 55.88; H, 6.08; N, 15.20.
1H NMR (DMSO-d6): d = 12.60 (br s, 1 H), 8.30–8.22 (m, 1 H),
8.20–8.16 (m, 1 H), 8.15–8.10 (m, 1 H), 8.08–7.95 (m, 2 H), 7.45–
7.40 (m, 1 H), 7.38–7.30 (m, 5 H), 7.25–7.18 (m, 5 H), 5.10–4.95
(m, 2 H), 4.52–4.45 (m, 1 H), 4.30–4.15 (m, 1 H), 4.10–3.95 (m,
1 H), 3.80–3.65 (m, 4 H), 3.05–3.00 (m, 1 H), 2.88–2.75 (m, 1 H),
1.65–1.60 (m, 1 H), 1.58–1.42 (m, 2 H), 1.30–1.25 (m, 1 H), 1.23
(d, J = 6.9 Hz, 3 H), 1.12 (d, J = 7.2 Hz, 3 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 174.0, 172.4, 171.2, 168.6, 168.4, 155.6,
137.6, 136.9, 129.3, 128.4, 128.0, 127.8, 126.2, 65.5, 53.9, 50.2,
48.4, 42.1, 41.7, 37.4, 24.3, 22.9, 21.4, 18.1.
Preparation of Pentapeptides 8a, 8b, hexapeptides 10, and
11a–d; General Procedure
N-(Protected tripeptidoyl)benzotriazole 2c (0.2 mmol) or N-(pro-
tected tetrapeptidoyl)benzotriazole 7a–d (0.2 mmol) were added at
0 °C to a solution of tripeptide 9a and/or amino acids 3b, 3j or
dipeptide 5a–c (0.2 mmol) in a mixture of MeCN (7 mL) and H2O
(3 mL) in the presence of Et3N (0.24 mmol). The reaction mixture
was then stirred at 0 °C until the starting material was completely
consumed as observed by TLC (hexanes–EtOAc, 2:1). HCl (4 N, 1
mL) was added and the solvent was removed under reduced pres-
sure. The residue obtained was dissolved in EtOAc (20 mL), and the
organic extract was washed with 4 M HCl (3 × 5 mL), brine (3 × 5
mL), and dried over anhydrous Na2SO4. Evaporation of the solvent
gave the desired products 8a, 8b, 10, and 11a–d.
Anal. Calcd for C33H44N6O9: C, 59.27; H, 6.63; N, 12.57. Found: C,
59.35; H, 6.67; N, 12.06.
Fmoc-L-Phe-L-Ala-L-Val-L-Leu-Gly-L-Ala-OH (11b)
Yield: 82%; white microcrystals (CH2Cl2–hexanes); mp 143.0–
145.0 °C.
1H NMR (DMSO-d6): d = 12.53 (br s, 1 H), 8.30–8.22 (m, 1 H),
8.25–8.14 (m, 1 H), 8.10–8.00 (m, 1 H), 7.87 (d, J = 7.5 Hz, 2 H),
7.65–7.50 (m, 3 H), 7.40 (t, J = 7.4 Hz, 2 H), 7.35–7.20 (m, 7 H),
7.20–7.12 (m, 1 H), 4.40–4.35 (m, 1 H), 4.30–4.22 (m, 2 H), 4.21–
4.16 (m, 1 H), 4.15–4.05 (m, 3 H), 3.75–3.65 (m, 1 H), 3.05–2.95
(m, 1 H), 2.80–2.70 (m, 1 H), 2.52–2.50 (m, 1 H), 2.50–2.47 (m,
1 H), 2.04–1.90 (m, 1 H), 1.65–1.55 (m, 1 H), 1.50–1.40 (m, 2 H),
1.30–1.15 (m, 6 H), 0.90–0.60 (m, 12 H).
Cbz-L-Ala-L-Phe-L-Gly-L-Ala-L-Phe-OH (8a)
Yield: 83%; white microcrystals (CH2Cl2); mp 193.0–195.0 °C.
1H NMR (DMSO-d6): d = 8.28–8.16 (m, 2 H), 8.04–7.90 (m, 2 H),
7.42 (d, J = 7.5 Hz, 1 H), 7.36–7.10 (m, 15 H), 5.10–4.90 (m, 2 H),
4.55–4.45 (m, 1 H), 4.48–4.25 (m, 2 H), 4.05–3.95 (m, 1 H), 3.71
(d, J = 5.1 Hz, 2 H), 3.10–3.00 (m, 2 H), 2.95–2.75 (m, 2 H), 1.20–
1.10 (m, 6 H).
13C NMR (DMSO-d6): d = 174.0, 172.3, 172.2, 171.4, 171.0, 168.4,
155.8, 143.7, 140.6, 138.2, 129.3, 128.0, 127.6, 127.0, 126.2, 125.3,
120.1, 65.7, 56.0, 48.2, 47.5, 46.6, 41.8, 40.7, 37.5, 24.3, 24.2, 23.2,
23.0, 21.7, 21.3, 19.2, 18.1, 17.9, 17.3.
13C NMR (DMSO-d6): d = 172.7, 172.3, 172.0, 171.2, 168.0, 155.6,
137.6, 137.5, 136.9, 129.2, 129.1, 128.3, 128.2, 128.0, 127.7, 126.4,
126.2, 65.5, 53.8, 53.5, 50.2, 47.8, 41.9, 37.5, 36.6, 18.4, 18.1.
Anal. Calcd for C34H39N5O8: C, 63.24; H, 6.09; N, 10.85. Found: C,
62.95; H, 6.13; N, 10.67.
Anal. Calcd for C43H54N6O9: C, 64.64; H, 6.81; N, 10.52. Found: C,
64.87; H, 7.06; N, 9.26.
HRMS (ESI+): m/z [M + Na]+ calcd for C43H54N6O9Na: 821.3844;
found: 821.3863; m/z [M – H + 2Na]+ calcd for C43H54N6O9Na2:
843.3664; found: 843.3664.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-OH (8b)
Yield: 86%; white microcrystals (MeOH); mp 236.0–238.0 °C.
1H NMR (DMSO-d6): d = 12.60 (br s, 1 H), 8.10 (d, J = 7.5 Hz,
1 H), 7.95–7.85 (m, 3 H), 7.45 (d, J = 7.2 Hz, 1 H), 7.36–7.28 (m,
5 H), 5.01 (s, 2 H), 4.30–4.16 (m, 4 H), 4.10–4.00 (m, 1 H), 1.65–
1.55 (m, 1 H), 1.50–1.40 (m, 2 H), 1.26 (d, J = 7.2 Hz, 3 H), 1.19
(d, J = 6.6 Hz, 9 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 173.9, 172.4, 171.8, 171.7, 171.6, 155.7,
137.0, 128.3, 127.7, 65.4, 50.9, 50.1, 48.0, 47.8, 47.4, 40.8, 24.1,
23.1, 21.6, 18.2, 18.0, 17.2.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-Gly-OH (11c)32
Yield: 87%; white microcrystals (MeOH); mp 240.0–242.0 °C.
1H NMR (DMSO-d6): d = 8.15–8.05 (m, 1 H), 8.00–7.90 (m, 4 H),
7.48–7.42 (m, 1 H), 7.38–7.30 (m, 5 H), 5.01 (s, 2 H), 4.30–4.20
(m, 4 H), 4.10–4.00 (m, 1 H), 3.75–3.65 (m, 2 H), 1.65–1.55 (m,
1 H), 1.50–1.40 (m, 2 H), 1.35–1.15 (m, 12 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 172.4, 172.3, 171.7, 171.6, 171.1, 155.6,
137.0, 128.3, 127.7, 65.4, 50.9, 50.1, 48.1, 47.9, 40.8, 24.1, 23.1,
21.6, 18.4, 18.1, 18.0.
Anal. Calcd for C26H39N5O8·H2O: C, 55.01; H, 7.28; N, 12.34.
Found: C, 55.53; H, 7.23; N, 12.14.
Cbz-L-Phe-L-Ala-L-Ala-Gly-L-Leu-L-Cys(S-Fm)-OH (10)
Yield: 61%; white microcrystals (MeOH); mp 194.0–196.0 °C.
Anal. Calcd for C28H42N6O9: C, 55.43; H, 6.98; N, 13.85. Found: C,
56.07; H, 7.36; N, 12.00.
1H NMR (DMSO-d6): d = 8.65–8.55 (m, 1 H), 8.35–8.28 (m, 1 H),
8.25–8.12 (m, 1 H), 8.10–8.05 (m, 1 H), 8.00–7.95 (m, 1 H), 7.88–
7.80 (m, 2 H), 7.78–7.70 (m, 2 H), 7.68–7.55 (m, 1 H), 7.45–7.10
(m, 10 H), 4.93 (br s, 1 H), 4.45–4.25 (m, 4 H), 4.20–4.10 (m, 1 H),
3.85–3.65 (m, 3 H), 3.18–3.05 (m, 3 H), 3.02–2.98 (m, 2 H), 2.80–
2.70 (m, 2 H), 1.65–1.55 (m, 1 H), 1.50–1.40 (m, 2 H), 1.28–1.10
(m, 3 H), 0.90–0.70 (m, 6 H).
HRMS (ESI+): m/z [M + Na]+ calcd for C28H42N6O9Na: 629.2905;
found: 629.2912; m/z [M – H + 2Na]+ calcd for C28H42N6O9Na2:
651.2725; found: 651.2729.
Cbz-L-Ala-L-Met-L-Ala-L-Ala-L-Ala-Gly-OH (11d)32
Yield: 84%; white microcrystals (CH2Cl2–hexanes); mp 254.0–
256.0 °C.
Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York

3004
A. Abdelmajeid et al.
PAPER
1H NMR (DMSO-d6): d = 12.60 (br s, 1 H), 8.18–8.10 (m, 1 H),
8.06–7.95 (m, 3 H), 7.92 (d, J = 7.8 Hz, 1 H), 7.50 (d, J = 7.5 Hz,
1 H), 7.40–7.30 (m, 5 H), 5.01 (s, 2 H), 4.38–4.20 (m, 4 H), 4.10–
4.00 (m, 1 H), 3.80–3.70 (m, 2 H), 2.45–2.40 (m, 2 H), 2.03 (s,
3 H), 1.95–1.75 (m, 2 H), 1.25–1.15 (m, 12 H).
dried over anhydrous Na2SO4. Evaporation of the solvent gave the
desired products 13, 14a, and 14b.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-L-Phe-OH (13)
Yield: 85%; white microcrystals (EtOH); mp 240.0–242.0 °C.
13C NMR (DMSO-d6): d = 172.5, 172.3, 171.8, 171.6, 171.1, 170.6,
155.7, 137.0, 128.3, 127.7, 65.4, 51.7, 50.1, 48.0, 47.9, 40.7, 32.1,
29.4, 18.4, 18.0, 14.6.
1H NMR (DMSO-d6): d = 8.12– 8.04 (m, 1 H), 7.98–7.82 (m, 4 H),
7.46 (d, J = 7.2 Hz, 1 H), 7.36–7.30 (m, 5 H), 7.26–7.16 (m, 5 H),
5.01 (s, 2 H), 4.45–4.35 (m, 1 H), 4.30–4.15 (m, 4 H), 4.10–4.00
(m, 1 H), 3.10–3.00 (m, 1 H), 2.95–2.85 (m, 1 H), 1.65–1.55 (m,
1 H), 1.50–1.40 (m, 2 H), 1.25–1.10 (m, 12 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 174.0, 172.8, 172.7, 172.0, 171.7, 171.5,
155.7, 137.4, 137.0, 129.2, 128.3, 128.2, 127.7, 126.4, 65.4, 53.5,
50.9, 50.1, 48.0, 47.8, 47.4, 40.8, 36.6, 24.1, 23.1, 21.6, 18.2, 18.1,
17.2.
Anal. Calcd for C27H40N6O9S·H2O: C, 50.46; H, 6.27; N, 13.08.
Found: C, 50.32; H, 6.44; N, 12.63.
Preparation of N-(Protected pentapeptidoyl)benzotriazoles 12a
and 12b; General Procedure
SOCl2 (1 mmol) was added to a solution of 1H-benzotriazole (4
mmol) in anhydrous THF or MeCN (15 mL) at 20 °C, and stirred
for 30 min. The reaction mixture was cooled to –30 °C, then N-pro-
tected pentapeptides 8a or 8b (1 mmol), dissolved in anhydrous
THF or MeCN (5 mL), were added dropwise and the mixture was
stirred for 4 h. The white precipitate that formed during the reaction
was filtered off, and the filtrate was concentrated under reduced
pressure. The residue obtained was washed with Et2O to remove ex-
cess BtH, then dried to give the desired products 12a and 12b.
Anal. Calcd for C35H48N6O9.2 H2O: C, 57.36; H, 7.15; N, 11.47.
Found: C, 57.46; H, 6.90; N, 11.64.
Cbz-L-Ala-L-Phe-L-Gly-L-Ala-L-Phe-L-Ala-Gly-OH (14a)
Yield: 82%; white microcrystals (CH2Cl2); mp 168.0–170.0 °C.
1H NMR (DMSO-d6): d = 12.65 (br s, 1 H), 8.28–8.16 (m, 2 H),
8.06–7.88 (m, 3 H), 7.44–7.32 (m, 7 H), 7.25–7.15 (m, 10 H), 5.08–
4.90 (m, 2 H), 4.55–4.45 (m, 2 H), 4.35–4.25 (m, 2 H), 4.05–3.95
(m, 1 H), 3.78–3.65 (m, 4 H), 3.05–2.95 (m, 2 H), 2.88–2.78 (m,
2 H), 1.26–1.10 (m, 9 H).
Cbz-L-Ala-L-Phe-L-Gly-L-Ala-L-Phe-Bt (12a)
Yield: 78%; white microcrystals (MeOH); mp 188.0–190.0 °C.
13C NMR (DMSO-d6): d = 172.7, 172.3, 172.0, 171.2, 170.5, 168.3,
168.0, 156.0, 137.5, 136.9, 129.2, 128.3, 128.2, 128.0, 127.7, 126.4,
126.2, 65.4, 53.8, 53.5, 50.1, 48.2, 47.8, 41.9, 37.5, 37.1, 18.7, 18.3,
18.1.
1H NMR (DMSO-d6): d = 8.95–8.85 (m, 1 H), 8.30–8.16 (m, 2 H),
8.04–7.95 (m, 2 H), 7.84–7.74 (m, 1 H), 7.65–7.58 (m, 1 H), 7.45–
7.10 (m, 17 H), 5.90–5.80 (m, 1 H), 5.10–4.95 (m, 2 H), 4.55–4.35
(m, 2 H), 4.10–3.95 (m, 1 H), 3.75–3.65 (m, 2 H), 3.35–3.30 (m,
1 H), 3.25–3.15 (m, 1 H), 3.08–3.00 (m, 1 H), 2.90–2.75 (m, 1 H),
1.25–1.05 (m, 6 H).
Anal. Calcd for C39H47N7O10: C, 60.53; H, 6.12. Found: C, 60.78;
H, 5.87.
13C NMR (DMSO-d6): d = 172.8, 172.3, 171.2, 171.0, 168.2, 155.6,
145.2, 137.6, 136.9, 136.5, 131.0, 130.4, 129.2, 129.0, 128.3, 128.0,
127.7, 126.7, 126.2, 120.2, 113.9, 65.4, 54.4, 53.8, 50.2, 47.6, 41.9,
37.4, 36.4, 18.2, 18.1.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-Gly-Gly-OH (14b)
Yield: 79%; white microcrystals; mp 263.0–265.0 °C.
1H NMR (DMSO-d6): d = 12.55 (br s, 1 H), 8.15–8.08 (m, 1 H),
8.00–7.86 (m, 4 H), 7.46 (d, J = 7.5 Hz, 1 H), 7.35 (br s, 6 H), 5.01
(s, 2 H), 4.30–4.20 (m, 3 H), 4.10–4.00 (m, 1 H), 3.76–3.70 (m,
1 H), 3.34 (s, 4 H), 1.65–1.55 (m, 1 H), 1.50–1.40 (m, 2 H), 1.19 (d,
J = 6.3 Hz, 12 H), 0.90–0.80 (m, 6 H).
Anal. Calcd for C40H42N8O7: C, 64.33; H, 5.67; N, 15.00. Found: C,
63.69; H, 5.60; N, 14.54.
Cbz-L-Ala-L-Leu-L-Ala-L-Ala-L-Ala-Bt (12b)
13C NMR (DMSO-d6): d = 173.9, 172.4, 171.7, 171.6, 171.5, 169.0,
155.6, 137.0, 128.3, 127.7, 65.3, 50.9, 50.1, 48.0, 47.8, 47.4, 40.7,
24.1, 23.1, 21.6, 18.1, 18.0, 17.1.
Yield: 85%; white microcrystals (CH2Cl2); mp 198.0–200.0 °C.
1H NMR (DMSO-d6): d = 8.51 (d, J = 6.9 Hz, 1 H), 8.29 (d, J =
8.1 Hz, 1 H), 8.23 (d, J = 8.1 Hz, 1 H), 7.98–7.85 (m, 3 H), 7.81 (t,
J = 7.2 Hz, 1 H), 7.64 (t, J = 8.1 Hz, 1 H), 7.45 (d, J = 7.5 Hz, 1 H),
7.38–7.28 (m, 5 H), 5.56 (t, J = 6.6 Hz, 1 H), 5.01 (s, 2 H), 4.45–
4.40 (m, 1 H), 4.30–4.20 (m, 2 H), 4.10–4.00 (m, 1 H), 1.65–1.55
(m, 1 H), 1.50–1.40 (m, 2 H), 1.25–1.10 (m, 9 H), 1.05–0.95 (m,
3 H), 0.90–0.80 (m, 6 H).
13C NMR (DMSO-d6): d = 172.5, 171.8, 155.7, 145.3, 137.0, 131.1,
130.6, 128.3, 127.7, 126.7, 120.2, 114.0, 65.4, 50.9, 50.1, 48.6,
48.0, 47.8, 47.6, 40.8, 24.1, 23.1, 21.6, 18.1, 17.2, 16.6.
Anal. Calcd for C30H45N7O11.H2O: C, 52.85; H, 6.95. Found: C,
52.54; H, 6.96.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.
Acknowledgment
Anal. Calcd for C32H42N8O7·H2O: C, 57.47; H, 6.63. Found: C,
57.52; H, 6.47.
We thank the University of Florida, The Kenan Foundation and
King Abdulaziz University (Jeddah, Saudi Arabia) for financial
support. Mr. A. Abdelmajeid is grateful to the higher education mi-
nistry in Egypt for a scholarship.
Preparation of Hexapeptide 13 and Heptapeptides 14a and 14b;
General Procedure
N-(Protected pentapeptidoyl)benzotriazole 12a or 12b (0.2 mmol)
was added at 0 °C to a solution of amino acid 3j or dipeptide 5c or
5d (0.2 mmol) in a mixture of MeCN (7 mL) and H2O (3 mL) in the
presence of Et3N (0.24 mmol). The reaction mixture was stirred at
0 °C until TLC (hexanes–EtOAc, 1:1) showed complete consump-
tion of the starting materials 12a or 12b, then 4 M HCl (1 mL) was
added and the solvent was removed under reduced pressure. The
residue obtained was dissolved in EtOAc (15 mL), and the organic
extract was washed with 4 M HCl (2 × 5 mL), brine (2 × 5 mL), and
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Synthesis 2011, No. 18, 2995–3005 © Thieme Stuttgart · New York