A facile and efficient method for synthesis of macrocyclic lipoglycopeptide

Article abstract of DOI:10.1016/j.tet.2014.12.097

An efficient and practical method for macrocyclic lipoglycopeptide synthesis was developed and utilized to synthesize lipoglycosylated derivatives of Tyrocidine A. The method is based on solid-phase peptide synthesis using 2-chlorotrityl resin as the soli

Full text of DOI:10.1016/j.tet.2014.12.097

Tetrahedron 71 (2015) 1018e1022
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A facile and efficient method for synthesis of macrocyclic
lipoglycopeptide
y
y
y
*
*
Qingjie Zhao , Xiang Li , Wenjuan Li , Yan Zou, Honggang Hu , Qiuye Wu
Department of Organic Chemistry, School of Pharmacy, Second Military Medical University, Shanghai 200433, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient and practical method for macrocyclic lipoglycopeptide synthesis was developed and utilized
to synthesize lipoglycosylated derivatives of Tyrocidine A. The method is based on solid-phase peptide
synthesis using 2-chlorotrityl resin as the solid-phase support and lipoglycosyl amino acids as building
blocks. This synthetic method should be generally applicable to various macrocyclic lipoglycopeptides.
Ó 2015 Elsevier Ltd. All rights reserved.
Received 27 November 2014
Received in revised form 25 December 2014
Accepted 29 December 2014
Available online 3 January 2015
Keywords:
Tyrocidine A
Lipoglycopeptide
Solid-phase peptide synthesis
Macrocyclic peptide
Glycosylation
1. Introduction
realized the first total synthesis of macrocyclic glycopeptides and
this method has been applied to prepare other macrocyclic glyco-
Lipoglycopeptide antibiotics are actinomycete-derived antibi-
otics with unique tricyclic or tetracyclic heptapeptide cores that are
usually glycosylated and sometimes have additional lipophilic fatty
acid side,1 such as telavancin2 and dalbavancin3 (Fig. 1). The gly-
copeptides antibiotics are the most important drugs in current use
for the treatment of Gram-positive bacterial infections.4 Dalba-
vancin and telavancin contain a heptapeptide core, common to all
glycopeptides, which enables them to inhibit transglycosylation
and transpeptidation (cell wall synthesis), and their lipophilic side
chains can prolong their half-life, help to anchor the agents to the
cell membrane and increase their activity against Gram-positive
cocci. In addition to inhibiting cell wall synthesis, telavancin and
oritavancin are also able to disrupt bacterial membrane integrity
and increase membrane permeability, oritavancin also inhibits RNA
synthesis.2,5 However, Lipoglycopeptides can only be acquired
through extraction of natural products,6 biotransformation,7 and
semisynthesis,8 which limit the application of lipoglycopeptides in
clinic.
peptides.10 However, chemical synthesis of macrocyclic lip-
oglycopeptide was not reported and attracted our attention.
Recently, great efforts have been made to obtain macrocyclic
peptides and their mimics.9 In 2009, our group has successfully
* Corresponding authors. Tel./fax: þ86 21 81871228 (H.H.); tel./fax: þ86 21
81871225 (Q.W.); e-mail addresses: huhonggang_fox@msn.com (H. Hu),
wuqy6439@sohu.com (Q. Wu).
y
These authors contributed equally to this work.
Figiure 1. Chemical structure of telavancin and dalbavancin.
http://dx.doi.org/10.1016/j.tet.2014.12.097
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

Q. Zhao et al. / Tetrahedron 71 (2015) 1018e1022
1019
Tyrocidine A is a cyclic decapeptide isolated from Bacillus bac-
teria that exhibits strong bactericidal activities and it has been
suggested to primarily target the bacterial membrane. In spite of its
severe side effects, Tyrocidine A represents an attractive lead
compound for the development of new antibacterial drugs.11
Herein, a facile and efficient method of synthesizing macrocyclic
lipoglycopeptide is described and four lipoglycosyl Tyrocidine A
derivatives were designed and synthesized. Further biological
evaluation was in progress (Fig. 2).
Scheme 1. Synthesis of full protected lipo-glyco asparagine derivatives.
10aed, as shown in Scheme 2, started from 2-amino-2-deoxy-D-
glucose hydrochloride 5. Firstly, 5 was transformed into compound
6 by well established procedures.14 Then, the free amino group was
protected with a 2,2,2-trichloroethoxycarbonyl (Troc) group, which
could be easily removed by zinc.15 The azide ethyl side chain was
introduced into the glucosamine using BF3$Et2O as a catalyst to
afford the compound 7. Next, the azido group was selectively re-
duced in the condition of Pd/C (10%)/CH3OH, followed by coupling
with Fmoc-Asp-OtBu to afford the compound glycosylated amino
acid 8. Further, when the Troc protected group was cleavaged in the
condition of Zn/CH3COOH, the free amino group can be coupled
with fatty acids to afford the key intermediate 9aed. Finally, the tBu
group was removed with TFA and the key intermediate 9aed were
converted into the full acetyl protected lipoglycosylated amino
acids 10aed.
Figiure 2. Chemical structure of Tyrocidine A lipoglycosylated derivatives.
2. Results and discussion
2.1. Synthetic design
Our plan was to first construct lipoglycosylated liner decapep-
tides by solid-phase peptide synthesis (SPPS) and then unite their
C-terminus and N-terminus via solution phase with good yield to
obtain macrocyclic lipoglycopeptides. It has been reported that
glycosylated amino acids could be directly used as building blocks,
just as other simple amino acids in the SPPS.12 Therefore, in our
research, the lipoglycosylated amino acids were directly coupled to
the peptide backbone for solid-phase lipoglycosylated liner pep-
tides assembly.
In addition, as the free amino and/or carboxylic groups within
their amino acid side chains contained in the title compounds, it
was necessary to fully protect the active group within the side
chains during the cyclization reaction, which ensured the efficiency
of the coupling reactions between the peptide C- and N-termini.13
In this regard, the extremely acid-sensitive 2-chlorotrityl resin
can be an applicable SPPS support, as peptides can be released from
this resin using 10% acetic acid, which does not affect the protecting
groups of amino acid side chains. Another advantage of using fully
protected glycopeptides for cyclic glycopeptide synthesis is that
these substrates would be easily soluble in organic solvents, which
should be particularly helpful for the cyclization reaction. On the
basis of the above considerations, we envisioned a synthetic
strategy as outlined in Scheme 1.
Scheme 2. The synthesis of full protected lipo-glyco amino acids. Reagents and con-
ditions: (a) 1,1,1-trichloro-2-(chloromethoxy) ethane, NaHCO3, DCM, 70%; (b) 2-
azidoethanol, BF.3Et2O, DCM, 68%; (c) Pd/C (10%), CH3OH, 78%; then Fmoc-Asp-OtBu,
DIC, HOBt, DCM, DMF, 48%; (d) Zn, CH3COOH; then lipo-acid, DIC, HOBt, DCM, DMF;
(e) TFA: DCM¼1:3.
2.3. Synthesis of the title compounds
From a retrosynthetic point of view, any peptide bond of the
cyclic peptide can be cleaved to offer a linear structure to work
with, so theoretically SPPS can start from any amino acid in the ring.
Practically, however, various synthetic plans can give different re-
sults.16 In the case of lipoglycopeptides synthesis, it is readily
imaginable that the lipoglycosylated amino acids should be in-
stalled at a later stage so as to reduce any potential interferences
caused by the lipo-glycans and to facilitate manual installation of
the lipoglycosylated amino acids, if necessary.
2.2. Synthetic design
Synthetic targets 10aed have monosaccharide with a long ali-
phatic chain attached to their asparagine side chain. They were key
intermediates for the synthesis of target compounds, and our first
undertaking was to prepare 10aed (Scheme 2). The synthesis of
In our synthesis of the title compounds, we chose to construct
the linear peptide/glycopeptides with 2-chlorotrityl resin as the
solid-phase support and Phe as the first amino acid to install.17 In

1020
Q. Zhao et al. / Tetrahedron 71 (2015) 1018e1022
this case, the full acetyl protected lipoglycosylated amino acids
10aed would be the second-to-last amino acid to be introduced
(Scheme 3). Thus, Phe was firstly anchored to the solid-phase
support via reacting trityl resin 11 with Fmoc-Phe-OH. Next, the
lipoglycosylated liner decapeptides were assembled via sequential
based on solid-phase peptide synthesis using 2-chlorotrityl resin as
the solid-phase support and lipoglycosylated amino acids as
building blocks. The cyclization reactions of these glycopeptides
gave the desired cyclic glycopeptides in practically quantitative
yields. This method was employed to synthesize four lip-
oglycosylated derivatives of tyrocidine A, and it should be appli-
cable to other macrocyclic lipoglycopeptides as well.
introduction of Fmoc-Pro-OH, Fmoc-
Fmoc-Orn(Boc)-OH, Fmoc-Val-OH, Fmoc-Tyr(tBu)-OH, Fmoc-
Gln(Trt)-OH, Asn derivatives 10aed, and Fmoc- -Phe-OH. Fully
D-Phe-OH, Fmoc-Leu-OH,
D
protected lipoglycosylated liner decapeptides assembly were
completely constructed by SPPS using 20% piperidine for the
deprotection of Fmoc and DCC and HOBt as the condensation re-
agents. The coupling processes were monitored by detecting Fmoc
released in each deprotection step, which suggested that all cou-
pling reactions were very effective. Finally, the loaded resins were
treated with 10% HOAc in trifluoroethanol (TFE) and DCM (1:8) to
give linear peptides 14aed. The released linear peptides were di-
rectly used in the next step without further purification.
4. Experimental section
4.1. General experimental methods
NMR spectra were recorded in CDCl3, CD3OD or DMSO-d6 unless
otherwise indicated with a Bruker AC-600P spectrometer, using
TMS as internal standard. ESI mass spectra were performed on an
API-3000 LC-MS spectrometer. HR-Q-TOF-MS were measured on an
Agilent 6538 UHD Accurate Mass Q-TOF LC/MS mass spectrometer.
Column chromatography was carried out on silica gel
(200e300 mesh). The solvents and reagents were used as received
or dried prior to use as needed. All reactions were monitored using
thin-layer chromatography (TLC) on silica gel plates. Detection was
effected by examination under UV light.
4.2. General procedure for full protected lipo-glyco amino
acids
4.2.1. 2-(2,2,2-Trichloroacetamido)-1,3,4,6-tetra-O-acetyl-2-deoxy-
b-D-glucopyranose 6. After NaHCO3 (2.2 g), compound 5 (5 g,
13.1 mmol) were dissolved in water (120 mL), and then 2,2,2-
trichloroethyl chloroformate (3.03 g, 14.3 mmol) was added
slowly at 0 ꢀC. The reaction mixture was stirred rt overnight. The
reaction was washed with water and extracted with DCM. The or-
ganic phase was dried over Na2SO4, and then condensed in vacuum
and solidified with ethyl ether to give the product 6 (3.6 g, 66%). 1H
NMR (300 MHz, CDCl3):
d
5.80 (d, J¼4.4 Hz, 1H), 5.43 (d, J¼4.7 Hz,
1H), 5.32 (t, J¼4.8 Hz, 1H), 5.18 (t, J¼4.8 Hz, 1H), 4.79 (s, 2H), 4.35
(dd, J¼6.2, 2.2 Hz, 1H), 4.19 (dd, J¼6.2, 0.8 Hz, 1H), 4.00 (t, J¼5.0 Hz,
1H), 3.93e3.90 (m, 1H), 2.17 (s, 3Hþ), 2.15 (s, 3H), 2.11 (s, 6H). HR-
QTOF-MS Calcd for
522.0388.
C
17H23Cl3NO11, (MþH)þ, 522.0331, found,
4.2.2. 2-Azidoethoxyl-2-(2,2,2-trichloroacetamido)-3,4,6-tri-O-ace-
tyl-2-deoxy- -glucopyranoside 7. After compound (3 g,
b
-D
6
Scheme 3. The synthesis of the title compounds. Reagents and conditions: (a) Fmoc-
Phe-OH, DIPEA, DCM; (b) Fmoc-amino acids, DCC, HOBt, DMF, DCM; (c) HOAc, TFE,
DCM (1: 2: 16); (d) PyBOP, HOBt, DIPEA, DCM; (e) TFA, Et3SiH, DCM (2: 1: 8); (f) MeOH,
MeONa.
5.76 mmol) was dissolved in DCM (40 mL), 2-Azidoethanol (1.43 g,
16.4 mmol) was added at 0 ꢀC. After 30 min, the BF3$Et2O (2.2 mL)
was added slowly and the reaction was stirred at 0 ꢀC for 1 h and
then at rt overnight. The reaction mixture was filtered and the fil-
trate was washed with saturated NaHCO3 and brine, dried over
Na2SO4, and concentrated in vacuum. The residue was purified on
a silica gel column (petroleum ether/EtOAc, 7:2) to give pure
product 7 as white solid (2.1 g, 68%). 1H NMR (300 MHz, CDCl3):
The cyclization of 14aed was realized via benzotriazol-1-
yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP),
HOBt, and DIPEA as the condensation reagents. The substrate linear
peptides 14aed were added very slowly (0.5 mg/ml) to the DCM
solution of condensation reagents to promote intramolecular re-
action. When MS results indicated that the cyclization reactions
were done and the linear peptides 14aed were transferred fully
into the cyclic peptides 15aed, the side chain protecting groups of
15aed were removed with 20% TFA in DCM containing 10% trie-
thylsilane (TES) and MeONa/MeOH (pH¼8) to afford the title
compound 1e4. The final products were thoroughly purified by
reverse phase HPLC to afford pure 1e4 in overall yields (15e22%,
starting from the step to load Phe onto the resin).
d
5.36 (t, J¼10.0 Hz, 1H), 5.21 (d, J¼8.7 Hz, 1H), 5.08 (t, J¼9.9 Hz, 1H),
4.84e4.75 (m, 2H), 4.61 (d, J¼8.7 Hz, 1H), 4.27 (dd, J¼12.4, 4.6 Hz,
1H), 4.14 (dd, J¼12.3, 2.4 Hz, 1H), 4.08e4.03 (m, 1H), 3.74e3.47 (m,
4H), 3.34e3.27 (m, 1H), 2.10 (s, 3H), 2.04 (s, 6H). HR-QTOF-MS Calcd
for C17H24Cl3N4Oþ10, (MþH)þ, 549.0553, found, 549.0558.
4.2.3. Glycosylated amino acid 8. After compound
7 (0.77 g,
1.48 mmol) was dissolved in CH3OH (15 mL),10% Pd/C (154 mg) was
added into the reaction and H2 was passed into the mixture over-
night. The reaction mixture was filtered and the filtrate was con-
centrated and dried in vacuum to give crude primary amine. Then,
Fmoc-Asp-OtBu (745 mg, 1.81 mmol) was dissolved in DCM (10 mL)
3. Conclusion
and DMF (1 mL), HOBt (305 mg, 2.26 mmol) and DIC (350
mL,
In summary, a highly efficient and versatile synthetic method
was developed for macrocyclic lipoglycopeptides. This method is
2.26 mmol) were added and the reaction was stirred for 40 min. The
obtained primary amine previously and DCM (30 mL) were added

Q. Zhao et al. / Tetrahedron 71 (2015) 1018e1022
1021
into the reaction mixture and the reaction was stirred overnight.
After the reaction was completed, the solution was concentrated
and the residue was purified on a silica gel column (petroleum
ether/EtOAc, 7:3) to give 8 as white solid, yield: 0.61 g, 48%. 1H NMR
4.29e4.25 (m, 2H), 4.19e4.12 (m, 2H), 4.02 (t, J¼9.8 Hz, 1H),
3.86e3.80 (m,1H), 3.74e3.70 (m,1H), 3.64e3.60 (m,1H), 3.46e3.41
(m, 1H), 3.36e3.28 (m, 1H), 2.84e2.69 (m, 2H), 2.64e2.59 (m, 2H),
2.20e2.11 (m, 2H), 2.09 (s, 3H), 2.01e1.95 (m, 10H), 1.61e1.54 (m,
2H), 1.49 (s, 9H), 1.40e1.25 (m, 14H), 0.95 (t, J¼6.9 Hz, 3H). HR-
(600 MHz, CDCl3):
d
7.77 (d, J¼7.5 Hz, 2H), 7.62 (d, J¼7.3 Hz, 2H),
7.41 (t, J¼7.4 Hz, 2H), 7.32 (t, J¼7.0 Hz, 2H), 6.18e6.12 (m, 1H),
5.89e5.58 (m, 2H), 5.21 (t, J¼9.7 Hz, 1H), 5.06 (t, J¼7.3 Hz, 1H),
4.82e4.80 (m, 1H), 4.72 (d, J¼12.1 Hz, 1H), 4.54e4.43 (m, 3H),
4.33e4.32 (m, 1H), 4.25 (t, J¼6.9 Hz, 2H), 4.16e4.12 (m, 1H),
3.90e3.85 (m, 1H), 3.63e3.54 (m, 4H), 3.32e3.25 (m, 1H),
2.98e2.86 (m, 1H), 2.71e2.66 (m, 1H), 2.08 (s, 3H), 2.01 (s, 6H), 1.51
(s, 9H). HR-QTOF-MS Calcd for C40H49Cl3N3Oþ15, (MþH)þ, 916.2224,
found, 916.2240.
QTOF-MS Calcd for
1004.5404.
C
55H78N3Oþ14
,
(MþH)þ, 1004.5478, found,
4.2.5. General synthetic procedure for glycosylated amino acid
10aed. After the full protected glycosylated amino acid (0.1 mmol)
was dissolved in TFA/DCM (1:3) (15 mL) and the reaction was
stirred for 1 h, the solution was concentrated and the residue was
purified on a silica gel column (DCM/MeOH, 15:1) to give pure
product 10aed as white solid.
4.2.4. General synthetic procedure for glycosylated amino acid
9aed. After compound 8 (0.6 mmol) was dissolved in CH3COOH
(10 mL), Zn (500 mg) was added and the reaction was stirred at rt
overnight. After the reaction was completed monitored by TLC,
CH3COOH was removed and the residue was washed with water
and extracted with DCM. The organic phase was dried over Na2SO4,
and then condensed in vacuum and used directly in next step. The
lipo acid (0.5 mmol) was dissolved in DCM (10 mL) and DMF (1 mL),
HOBt (0.5 mmol) and DIC (0.5 mmol) were added and the reaction
was stirred for 40 min. Then the amine obtained previously
(0.5 mmol) were added into the reaction mixture and the reaction
was stirred overnight. After the reaction was completed, the solu-
tion was concentrated and the residue was purified on a silica gel
column (DCM/MeOH, 25:1) to give pure product.
Compound 10a: Yield 85%. 1H NMR (600 MHz, DMSO):
d 7.95 (d,
J¼7.5 Hz, 2H), 7.93e7.86 (m, 2H), 7.75 (d, J¼7.4 Hz, 2H), 7.55 (s, 1H),
7.47 (t, J¼7.5 Hz, 2H), 7.38 (t, J¼7.4 Hz, 2H), 5.14 (t, J¼9.3 Hz, 1H),
4.88 (t, J¼9.4 Hz, 1H), 4.69 (d, J¼8.5 Hz, 1H), 4.43e4.35 (m, 1H),
4.34e4.29 (m, 2H), 4.29e4.20 (m, 2H), 4.09e4.02 (m, 1H),
3.91e3.85 (m, 1H), 3.85e3.77 (m, 1H), 3.74e3.67 (m, 1H), 3.58e3.52
(m, 1H), 3.32e3.26 (m, 1H), 3.24e3.17 (m, 1H), 2.68e2.62 (m, 1H),
2.54e2.48 (m, 1H), 2.09e2.04 (m, 5H), 2.02 (s, 3H), 1.94 (s, 3H),
1.53e1.43 (m, 2H), 1.30e1.24 (m, 20H), 0.89 (t, J¼6.9 Hz, 3H). HR-
QTOF-MS Calcd for
896.4552.
C
47H66N3Oþ14
,
(MþH)þ, 896.4539, found,
Compound 10b: Yield 83%. 1H NMR (600 MHz, DMSO):
d 7.94 (d,
J¼7.5 Hz, 2H), 7.93e7.86 (m, 2H), 7.75 (d, J¼7.4 Hz, 2H), 7.55 (s, 1H),
7.47 (t, J¼7.5 Hz, 2H), 7.38 (t, J¼7.4 Hz, 2H), 5.14 (t, J¼9.2 Hz, 1H),
4.88 (t, J¼9.5 Hz, 1H), 4.68 (d, J¼8.7 Hz, 1H), 4.43e4.30 (m, 2H),
4.29e4.21 (m, 2H), 4.09e4.03 (m, 1H), 3.91e3.85 (m, 1H),
3.83e3.78 (m, 1H), 3.73e3.67 (m, 1H), 3.59e3.52 (m, 1H),
3.32e3.26 (m, 1H), 3.24e3.17 (m, 1H), 2.68e2.60 (m, 1H), 2.54e2.47
(m, 1H), 2.09e2.03 (m, 5H), 2.01 (s, 3H), 1.94 (s, 3H), 1.52e1.45 (m,
2H), 1.31e1.25 (m, 24H), 0.92e0.89 (m, 3H). HR-QTOF-MS Calcd for
Compound 9a: Yield 262 mg, 55%. 1H NMR (600 MHz, MeOD):
d
7.80 (d, J¼7.5 Hz, 2H), 7.60 (d, J¼7.4 Hz, 2H), 7.56 (s, 1H), 7.43 (t,
J¼7.3 Hz, 2H), 7.34 (t, J¼7.4 Hz, 2H), 5.21 (t, J¼9.6 Hz, 1H), 5.05 (t,
J¼9.5 Hz, 1H), 4.58 (d, J¼8.5 Hz, 1H), 4.51e4.48 (m, 1H), 4.45e4.42
(m, 1H), 4.38e4.35 (m, 1H), 4.31e4.26 (m, 2H), 4.19e4.12 (m, 1H),
4.00 (t, J¼9.8 Hz, 1H), 3.89e3.82 (m, 1H), 3.78e3.72 (m, 1H),
3.67e3.62 (m,1H), 3.50e3.42 (m,1H), 3.35e3.31 (m,1H), 2.82e2.72
(m, 2H), 2.20e2.14 (m, 2H), 2.10 (s, 3H), 2.05 (s, 3H), 2.03 (s, 3H),
1.62e1.56 (m, 2H), 1.50 (s, 9H), 1.34e1.25 (m, 20H), 0.91 (t, J¼6.9 Hz,
3H). HR-QTOF-MS Calcd for C51H74N3Oþ14, (MþH)þ, 952.5165, found,
952.5184.
C
49H70N3Oþ14, (MþH)þ, 924.4852, found, 924.4885.
Compound 10c: Yield 90%. 1H NMR (600 MHz, MeOD):
d
7.95 (d,
J¼7.5 Hz, 2H), 7.93e7.86 (m, 2H), 7.75 (d, J¼7.4 Hz, 2H), 7.58 (d,
J¼7.1 Hz, 1H), 7.47 (t, J¼7.3 Hz, 2H), 7.38 (t, J¼7.4 Hz, 2H), 5.42e5.31
(m, 2H), 5.13 (t, J¼9.5 Hz, 1H), 4.88 (t, J¼9.7 Hz, 1H), 4.69 (d,
J¼8.6 Hz, 1H), 4.44e4.37 (m, 1H), 4.34e4.20 (m, 4H), 4.09e4.02 (m,
1H), 3.90e3.84 (m, 1H), 3.83e3.77 (m, 1H), 3.73e3.66 (m, 1H),
3.59e3.52 (m,1H), 3.32e3.27 (m, 1H), 3.23e3.18 (m, 1H), 2.69e2.62
(m, 1H), 2.10e1.98 (m, 12H), 1.52e1.44 (m, 2H), 1.36e1.2þ3 (m, 20H),
0.90 (t, J¼7.1 Hz, 3H). HR-QTOF-MS Calcd for C51H72N3O14, (MþH)þ,
950.5009, found, 950.4990.
Compound 9b: Yield 284 mg, 58%. 1H NMR (600 MHz, MeOD):
d
7.78 (d, J¼7.5 Hz, 2H), 7.63 (d, J¼7.4 Hz, 2H), 7.52 (s, 1H), 7.40 (t,
J¼7.3 Hz, 2H), 7.34 (t, J¼7.5 Hz, 2H), 5.20 (t, J¼9.5 Hz, 1H), 5.03 (t,
J¼9.6 Hz, 1H), 4.54 (d, J¼8.4 Hz, 1H), 4.53e4.47 (m, 1H), 4.45e4.42
(m, 1H), 4.38e4.35 (m, 1H), 4.31e4.26 (m, 2H), 4.19e4.12 (m, 1H),
4.02 (t, J¼9.8 Hz, 1H), 3.89e3.84 (m, 1H), 3.79e3.72 (m, 1H),
3.68e3.62 (m, 1H), 3.50e3.42 (m, 1H), 3.35e3.31 (m, 1H),
2.92e2.84 (m, 2H), 2.22e2.14 (m, 2H), 2.12 (s, 3H), 2.08 (s, 3H), 2.03
(s, 3H), 1.65e1.54 (m, 2H), 1.52 (s, 9H), 1.36e1.22 (m, 24H), 0.89 (t,
J¼6.9 Hz, 3H). HR-QTOF-MS Calcd for C53H78N3Oþ14, (MþH)þ,
980.5484, found, 980.5434.
Compound 10d: Yield 88%. 1H NMR (600 MHz, MeOD):
d 7.94 (d,
J¼7.5 Hz, 2H), 7.92e7.88 (m, 2H), 7.75 (d, J¼7.4 Hz, 2H), 7.60 (d,
J¼7.1 Hz, 1H), 7.47 (t, J¼7.3 Hz, 2H), 7.38 (t, J¼7.4 Hz, 2H), 5.47e5.34
(m, 4H), 5.13 (t, J¼9.5 Hz, 1H), 4.88 (t, J¼9.7 Hz, 1H), 4.69 (d,
J¼8.6 Hz, 1H), 4.49e4.45 (m, 1H), 4.45e4.38 (m, 1H), 4.35e4.31 (m,
2H), 4.29e4.25 (m, 2H), 4.16e4.12 (m, 2H), 4.02 (t, J¼9.4 Hz, 1H),
3.86e3.80 (m,1H), 3.74e3.70 (m,1H), 3.64e3.60 (m,1H), 3.46e3.41
(m, 1H), 3.36e3.28 (m, 1H), 2.84e2.69 (m, 2H), 2.66e2.59 (m, 2H),
2.19e2.13 (m, 2H), 2.12e2.08 (m, 4H), 2.01e1.95 (m, 9H), 1.57e1.44
(m, 2H), 1.40e1.25 (m, 14H), 0.95 (t, J¼6.9 Hz, 3H). HR-QTOF-MS
Calcd for C51H70N3Oþ14, (MþH)þ, 948.4852, found, 948.4870.
Compound 9c: Yield 287 mg, 57%. 1H NMR (600 MHz, MeOD):
d
7.78 (d, J¼7.5 Hz, 2H), 7.64 (d, J¼7.4 Hz, 2H), 7.43 (s, 1H), 7.41 (t,
J¼7.3 Hz, 2H), 7.33 (t, J¼7.4 Hz, 2H), 5.39e5.33 (m, 2H), 5.18 (t,
J¼9.5 Hz, 1H), 5.04 (t, J¼9.7 Hz, 1H), 4.55 (d, J¼8.4 Hz, 1H),
4.49e4.47 (m,1H), 4.45e4.40 (m,1H), 4.37e4.31 (m, 2H), 4.29e4.25
(m, 2H), 4.17e4.12 (m, 2H), 3.99 (t, J¼9.8 Hz,1H), 3.86e3.82 (m, 1H),
3.74e3.70 (m,1H), 3.64e3.58 (m,1H), 3.46e3.41 (m,1H), 3.36e3.30
(m, 1H), 2.84e2.69 (m, 2H), 2.20e2.11 (m, 2H), 2.09 (s, 3H),
2.07e2.00 (m, 10H), 1.61e1.54 (m, 2H), 1.49 (s, 9H), 1.40e1.25 (m,
4.3. Synthesis of the title compounds 1e4 (common
procedures)
20H), 0.91 (t, J¼6.9 Hz, 3H). HR-QTOF-MS Calcd for C55H80N3O1þ4
,
(MþH)þ, 1006.5635, found, 1006.5684.
After a mixture of trityl resin 11 (100 mg, 0.1 mmol) and Fmoc-
Phe-OH (98 mg, 0.24 mmol) was shaken on a vortex mixer at rt for
0.5 h, the resin was filtered off and washed several times with
MeOH and DCM. Then piperidine/DMF(v/v, 1:4) (10 mL) was added
and the resin was shaken at rt for 3 h. The resin was filtered off and
washed several times with DCM to give the product 12. Then HOBt
Compound 9d: Yield 266 mg, 53%. 1H NMR (600 MHz, MeOD):
7.80 (d, J¼7.5 Hz, 2H), 7.64 (d, J¼7.4 Hz, 2H), 7.47 (s, 1H), 7.45 (t,
d
J¼7.3 Hz, 2H), 7.33 (t, J¼7.4 Hz, 2H), 5.49e5.37 (m, 4H), 5.18 (t,
J¼9.5 Hz, 1H), 5.09 (t, J¼9.7 Hz, 1H), 4.59 (d, J¼8.4 Hz, 1H),
4.49e4.45 (m, 1H), 4.45e4.39 (m, 1H), 4.35e4.31 (m, 2H),

1022
Q. Zhao et al. / Tetrahedron 71 (2015) 1018e1022
(40 mg, 0.3 mmol), Fmoc-Pro-OH (67 mg, 0.2 mmol) and DCC
(62 mg, 0.3 mmol) were dissolved in DCM (8 mL) and DMF (2 mL)
and stirred for 0.5 h, the residue was mixed with the resin and the
resin was shaken for 3 h. After that, the resin was filtered off and
washed several times with DMF and DCM, and then piperidine/
DMF(v/v, 1:4) (10 mL) was added and the resin was shaken at rt for
3 h. The resin was filtered off and washed several times with DCM,
here the first Pro had been loaded on the resin. Then amino acids
4.24e4.15 (m, 5H), 4.11e4.05 (m, 2H), 3.81e3.50 (m, 3H), 3.29e3.21
(m, 17H), 2.85e2.46 (m, 5H), 2.24 (t, J¼7.6 Hz, 6H), 2.05 (s, 8H),
1.62e1.33 (m, 20H), 1.08e0.92 (m, 9H), 0.58e0.51 (m, 6H). HR-
QTOF-MS Calcd for C92H135N14Oþ19, (MþH)þ, 1741.0095, found,
1741.0041.
Title compound 4, retention time: 22 min, white solid (9.5 mg,
19%). 1H NMR (600 MHz, MeOD):
d 9.23e8.57 (m, 11H), 7.92e7.01
(m, 19H), 6.72e6.67 (m, 1H), 6.47e6.43 (m, 1H), 5.50e5.26 (m, 6H),
4.94e4.78 (m, 5H), 4.59e4.24 (m, 5H), 4.24e3.96 (m, 3H),
3.43e3.32 (m, 20H), 2.73e2.68 (m, 2H), 2.40e2.09 (m, 7H),
1.91e1.61 (m, 18H), 1.60e1.41 (m, 3H), 1.41e1.05 (m, 14H), 1.19e1.00
Fmoc-
Fmoc-Tyr(tBu)-OH, Fmoc-Gln(Trt)-OH, full protected lipo-glyco
amino acids 10aed and Fmoc- -Phe-OH were sequentially loaded
D-Phe-OH, Fmoc-Leu-OH, Fmoc-Orn(Boc)-OH, Fmoc-Val-OH,
D
to construct the resins, which contains the linear lipo-glyco pep-
tides 13aed.
(m, 9H), 0.89e0.54 (m, 6H). HR-QTOF-MS Calcd for C92H133N14O1þ9
(MþH)þ, 1738.9938, found, 1738.9932.
,
To cleave the linear peptides from the resin, the lipo-glyco
peptide loaded resin was treated with a mixture of HOAc and TFE
in DCM (1:2:16, 15 mL) for 1 h at rt. The resin was filtered off and
was washed with DCM. The washings were combined and con-
densed together with toluene three times in vacuum to give 14aed.
These crude products were applied to cyclization without any
purification.
Acknowledgements
We are grateful to the National Natural Science Foundation of
China (No. 20902109, 21402235), State Project for Essential Drug
Research and Development (2012ZX09J12108-01, 2012ZX09502-
001-005), Shanghai Leading Academic Discipline Project (B906),
and Instrumental Analysis Center of our university for NMR spec-
troscopic and mass spectrometric analyses.
For lipo-glyco peptides cyclization, when PyBOP (3 equiv), HOBt
(3 equiv) and DIPEA (6 equiv) were dissolved in DCM (200 mL) in
a round-bottom flask, compounds 14aed that dissolved in DCM
(0.5 mg/ml) were added to the solution over a period of 4 h. After
the addition was finished, the mixture was stirred at rt overnight.
Then, DCM was removed and the resulting residue was briefly
purified by Sephadex LH-20 to afford 15aed. Compounds 15aed
were dissolved in TFA/DCM/Et3SiH (2:8:1) (15 mL) and the reaction
was stirred at rt for 1 h. Then the reaction mixture was concen-
trated to dryness. At last, the residues were dissolved in MeONa/
MeOH (pH¼8) (15 mL), the reaction was stirred at rt for another
hour, and then the solution was concentrated in vacuum, finally the
residues were purified by HPLC (Supelco Discovery C18
250 mmꢁ25 mm column, Solution A was 0.1% TFA in water, and
solution B was 0.1% TFA in MeCN. Gradient: A linear gradient of
25%e25% B in first 5 min, then a linear gradient of 25%e90% B in
5e30 min, then 90% in last 10 min, 10 mL/min) to give title com-
pounds 1e4.
Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.12.097.
References and notes
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Clin. Infect. Dis. 2012, 55, S71eS76.
ꢀ
Title compound 1, retention time: 16 min, white solid (7.5 mg,
19%). 1H NMR (600 MHz, MeOD):
d 7.88e6.45 (m, 19H), 5.84 (s, 1H),
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5.44 (s, 1H), 4.95 (s, 1H), 4.74 (s, 1H), 4.68e4.57 (m, 3H), 4.49 (s, 1H),
4.39 (d, J¼7.4 Hz, 1H), 4.21e4.16 (m, 1H), 4.13e4.09 (m, 1H), 3.84 (d,
J¼10.0 Hz, 2H), 3.81e3.63 (m, 4H), 3.62e3.57 (m, 1H), 3.56e3.51
(m, 1H), 3.45 (t, J¼10.0 Hz, 1H), 3.36e3.32 (m, 2H), 3.30e3.17 (m,
6H), 3.09e3.02 (m, 2H), 2.89e2.80 (m, 1H), 2.49e2.41 (m, 1H),
2.27e2.17 (m, 5H), 2.10e1.83 (m, 7H), 1.78e1.70 (m, 2H), 1.64e1.49
(m, 5H), 1.45e1.22 (m, 32H), 1.20e1.þ05 (m, 9H), 0.98e0.5 (m, 6H).
HR-QTOF-MS Calcd for C88H129N14O19, (MþH)þ, 1686.9626, found
1686.9624.
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Title compound 2, retention time: 20 min, white solid (6.5 mg,
22%). 1H NMR (600 MHz, MeOD):
d 7.92e6.44 (m, 19H), 5.89 (d,
J¼11.1 Hz, 1H), 5.56e5.49 (m, 1H), 5.05e5.02 (m, 1H), 4.81e4.77 (m,
2H), 4.72e4.62 (m, 4H), 4.57e4.52 (m, 2H), 4.39 (d, J¼9.8 Hz, 1H),
4.23e4.12 (m, 2H), 3.87e3.86 (m,1H), 3.84e3.81 (m,1H), 3.80e3.76
(m, 1H), 3.75e3.71 (m, 1H), 3.69e3.65 (m, 1H), 3.62e3.56 (m, 2H),
3.48e3.42 (m, 2H), 3.36e3.23 (m, 5H), 3.20 (s, 1H), 3.12e3.06 (m,
1H), 2.91e2.83 (m, 1H), 2.51e2.44 (m, 1H), 2.33e2.16 (m, 5H),
2.11e2.02 (m, 2H), 1.88e1.81 (m, 4H), 1.76e1.67 (m, 3H), 1.63e1.57
(m, 2H), 1.54e1.48 (m, 1H), 1.41e1.25 (m, 29H), 1.26e1.14 (m,12H),
15. Hansen, S. G.; Skrydstrup, T. Eur. J. Org. Chem. 2007, 20, 3392e3401.
16. Wadhwani, P.; Afonin, S.; Ieronimo, M.; Buerck, J.; Ulrich, A. S. J. Org. Chem.
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17. Dedola, S.; Izumi, M.; Makimura, Y.; Seko, A.; Kanamori, A.; Sakono, M.; Ito, Y.;
Kajihara, Y. Angew. Chem., Int. Ed. 2014, 53, 2883e2887; Hudak, J.; Yu, H.; Ber-
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0.96 (t, J¼7.0 Hz, 3H). HR-QTOF-MS Calcd for C90H133N14O1þ9
,
(MþH)þ, 1714.9939, found 1714.9902.
Title compound 3, retention time: 23 min, white solid (7.0 mg,
15%). 1H NMR (600 MHz, MeOD):
d 9.30e8.38 (m, 11H), 7.75e7.25
(m, 19H), 6.97e6.91 (m, 1H), 6.74e6.66 (m, 1H), 5.88e5.63 (m, 3H),
5.40e5.35 (m, 1H), 4.71e4.65 (m, 4H), 4.40 (d, J¼7.8 Hz, 1H),