Synthesis of modified carboxyl binding pockets of vancomycin and teicoplanin

Article abstract of DOI:10.1021/jo961412m

Sixteen-membered macrocycle 3 and 16+14 bicyclic compound 4, incorporating a terminal primary hydroxyl group in the peptide sequence, have been designed and synthesized. The syntheses feature the use of an efficient cycloetherification based on an intramolecular S(N)Ar reaction for the formation of biaryl ether bonds. Cyclization of linear tetrapeptide 30, prepared via a convergent [2+2] segment coupling between 26 and 29, gave macrocycle 31 (P configuration) as a single isolable atropisomer. Removal of the Boc protecting group afforded the modified carboxyl binding pocket of vancomycin 3. A sequential 2-fold intramolecular S(N)Ar reaction has been used to construct the model bicyclic system (i.e. 4) of the D-O-E-F-O-G ring of teicoplanin. Cyclization conditions (CsF, DMF, room temperature) are sufficiently mild that the configuration of the racemization-prone arylglycine residue was not affected. Chiral building blocks such as D-(1R)-[2-[(tert-butyldimethylsilyl)oxy]1-[3-(allyloxy)phenyl]ethyl]am ine 16, and L-(S)-N-Boc-[3-(isopropyloxy)phenyl]glycine (32) were synthesized employing Evans' asymmetric azidation method, while L-(S)-4-fluoro-3-nitrophenylalanine methyl ester 23 was prepared using Schollkopf's bislactim ether as chiral glycine template. Compound 3 showed interesting conformational properties compared to vancomycin and its binding with Ac-D-Ala was studied by NMR titration experiments. A dissociation constant (Kd) = 5 x 10^-4) was calculated by a curve fitting method. Compound 4 is currently the most advanced synthetic intermediate toward the total synthesis of teicoplanin.

Full text of DOI:10.1021/jo961412m

J . Org. Chem. 1996, 61, 9309-9322
9309
Syn th esis of Mod ified Ca r boxyl Bin d in g P ock ets of Va n com ycin
a n d Teicop la n in †
Miche`le Bois-Choussy, Luc Neuville, Rene´ Beugelmans, and J ieping Zhu*
Institut de Chimie des Substances Naturelles, CNRS, 91198 Gif-sur-Yvette, France
Received J uly 24, 1996X
Sixteen-membered macrocycle 3 and 16+14 bicyclic compound 4, incorporating a terminal primary
hydroxyl group in the peptide sequence, have been designed and synthesized. The syntheses feature
the use of an efficient cycloetherification based on an intramolecular SNAr reaction for the formation
of biaryl ether bonds. Cyclization of linear tetrapeptide 30, prepared via a convergent [2+2] segment
coupling between 26 and 29, gave macrocycle 31 (P configuration) as a single isolable atropisomer.
Removal of the Boc protecting group afforded the modified carboxyl binding pocket of vancomycin
3. A sequential 2-fold intramolecular SNAr reaction has been used to construct the model bicyclic
system (i.e. 4) of the D-O-E-F -O-G ring of teicoplanin. Cyclization conditions (CsF, DMF, room
temperature) are sufficiently mild that the configuration of the racemization-prone arylglycine
residue was not affected. Chiral building blocks such as D-(1R)-[2-[(tert-butyldimethylsilyl)oxy]-
1-[3-(allyloxy)phenyl]ethyl]amine 16, and L-(S)-N-Boc-[3-(isopropyloxy)phenyl]glycine (32) were
synthesized employing Evans’ asymmetric azidation method, while L-(S)-4-fluoro-3-nitrophenyl-
alanine methyl ester 23 was prepared using Scho¨llkopf’s bislactim ether as chiral glycine template.
Compound 3 showed interesting conformational properties compared to vancomycin and its binding
with Ac-D-Ala was studied by NMR titration experiments. A dissociation constant (Kd ) 5 × 10-4
)
was calculated by a curve fitting method. Compound 4 is currently the most advanced synthetic
intermediate toward the total synthesis of teicoplanin.
In tr od u ction
The glycopeptide group of antibiotics,1 exemplified by
vancomycin (1) and teicoplanin (2) (Figure 1), is impor-
tant in the treatment of infections caused by Gram-
positive organisms, especially those which are â-lactam
resistant. The antibacterial activity of this family of
antibiotics arises from specific binding of the glycopeptide
to bacterial cell wall precursors terminating in the
sequence D-Ala-D-Ala.2 After more than 30 years of clinic
use, resistance to drugs of vancomycin family has been
recognized since the late 1980s. Biosynthesis of a D-Ala-
D-lactate depsipeptide and its incorporation as the ter-
minal peptidoglycan of resistant bacteria has been pro-
posed as the principal mechanism of resistance.3 Since
vancomycin-resistant enterococci (VRE) also carry resis-
tance to virtually all other known antibiotics, the prog-
nosis for patients with such refractory infections is grim.
† Dedicated to Professor Dieter Seebach on the occasion of his 60th
birthday.
X Abstract published in Advance ACS Abstracts, December 1, 1996.
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This growing problem of resistance has recently rekindled
interest in this field.4
The complex structure of vancomycin makes it a
challenging synthetic target.5 Since the first successful
S0022-3263(96)01412-0 CCC: $12.00 © 1996 American Chemical Society

9310 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
synthesis of a model C-O-D ring of vancomycin by
Hamilton’s group in 1986,6 remarkable achievements
have been registered in recent years. Biomimetic syn-
thesis of bicyclic C-O-D-O-E ring by Evans’ 7 and Yama-
mura’s group8 as well as Evans’ brilliant, and until now,
only synthesis of the 12-membered AB fragment9 il-
lustrate the notable progress made toward the long
awaited total synthesis of vancomycin.
Recent work in our laboratory has demonstrated that
the intramolecular nucleophilic aromatic substitution (SN-
Ar)10 reaction offers an exceptionally efficient method of
synthesizing macrocycles containing a biaryl ether bridge.
Biaryl ether formation with concomitant ring closure
under extremely mild conditions (K2CO3 or CsF, DMF,
rt) constitutes the basic strategy of our approach.11 This
method has been successfully applied to the synthesis of
the naturally occurring 17-membered cyclic tripeptide
K-13,12 16-membered vancomycin models,13 14-membered
teicoplanin,14 and bouvardin models.15 Shortly after the
disclosure of our work, other groups, notably, those of
Rama Rao,16 Boger,17 Rich,18a Pearson,18b and very re-
cently Evans,19 have employed this methodology in the
realization of their synthetic strategies.
F igu r e 2.
In the search for synthetic analogs having enhanced
affinity toward the D-Ala-D-lactate, we have designed
molecules 3 and 4 (Figure 2) as modified carboxyl binding
pockets of antibiotics.20 We hypothesized that the pri-
mary hydroxy group of compounds 3 and 4 could, a priori,
lead to increased affinity toward N-Ac-D-Ala-D-lactate.
This polar function may be considered as a hydrogen-
bond donor which, if the solution conformation permitted,
could form a hydrogen bond with the ester function
(hydrogen acceptor) of D-Ala-D-lactate, thus restoring the
four hydrogen bonds required for inhibiting cell wall
biosynthesis of modified peptidoglycan in vancomycin-
resistant bacteria. Hamilton et al.21 have recently re-
ported a new family of neutral, multidentate receptors
for carboxylate recognition and have demonstrated a
dramatic increase in binding affinity when a hydroxyl
group was incorporated in their receptor. The present
paper details the successful synthesis of compounds 3 and
4 and presents additional peripheral observations re-
corded along the way.
(4) (a) Malabarba, A.; Ciabatti, R. J . Med. Chem. 1994, 37, 2988-
2990. (b) Malabarba, A.; Ciabatti, R.; Kettenring, J .; Ferrari, P.; Vekey,
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Wu, Z.; Walsh, C. T. Proc. Nat. Acad. Sci. U.S.A. 1995, 92, 11603-
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(5) For a recent comprehensive review, see: Rama Rao, A. V.;
Gurjar, M. K.; Reddy, L.; Rao, A. S. Chem. Rev. 1995, 95, 2135-2167.
(6) Synthesis of 16-membered vancomycin models via macrolactam-
ization, see: (a) Mann, M. J .; Pant, N.; Hamilton, A. D. J . Chem. Soc.,
Chem. Commun. 1986, 158-160. (b) Pant, N.; Hamilton, A. D. J . Am.
Chem. Soc. 1988, 110, 2002-2003. (c) Crimmin, M. J .; Brown, A. J .
Tetrahedron Lett. 1990, 31, 2021-2024. (d) Stone, M. J .; Van Dyk, M.
S.; Booth, P. M.; Williams, D. H. J . Chem. Soc., Perkin Trans. I 1991,
1629-1635. (e) Pearson, A. J .; Park, J . G. J . Org. Chem. 1992, 57,
1744-1752. (f) Pearson, A. J .; Lee, K. J . Org. Chem. 1995, 60, 7153-
7160.
Resu lts a n d Discu ssion
Syn th esis of D-O-E Rin g 3. Our strategy for the
synthesis of 3, illustrated in Scheme 1, features an
intramolecular SNAr reaction as the key ring closure step.
D-(R)-[3-(allyloxy)phenyl]glycine methyl ester was pre-
pared using Evans’ asymmetric electrophilic azidation
method22 as depicted in Scheme 2. Allyl protection of (3-
hydroxyphenyl)acetic acid (8) followed by incorporation
of chiral auxiliary R-10 via the mixed anhydride method
afforded imide 11. Azidation employing a modified work-
up procedure afforded 12. The de of this reaction was
higher than 85% and two diastereoisomers were readily
separated by careful flash chromatography. Treatment
of 12 with LiOOH gave the R-azido acid 13 which was
immediately transformed into methyl ester 14. Reduc-
tion of 14 with SnCl2 in methanol23 afforded R-amino
ester 15 whose optical purity (95%) was determined by
transformation into its (S)-lactamide derivative 17. We
noted that transesterification of 12 using magnesium
methoxide led to significant racemization. Conversion
(7) Evans, D. A.; Elleman, J . A.; Devries, K. M. J . Am. Chem. Soc.
1989, 111, 8912-8914.
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1989, 30, 6043-6046. (b) Nakamura, K.; Nishiyama, S.; Yamamura,
S. Tetrahedron Lett. 1995, 36, 8621-8624.
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J . Am. Chem. Soc. 1993, 115, 6426-6427. (b) Evans, D. A.; Dinsmore,
C. J . Tetrahedron Lett. 1993, 34, 6029-6032.
(10) For recent books and reviews, see: (a) Terrier, F. Nucleophilic
Aromatic Displacement: The Role of the Nitro Group; VCH: New York,
1991; Chapter 1. (b) Paradisi, C. Arene Substitution via Nucleophilic
Addition to Electron Deficient Arenes. Comprehensive Organic Syn-
thesis; Pergamon Press: Oxford, 1991; Vol. 4, pp 423-450. (c) Vlasov,
V. M. J . Fluorine Chem. 1993, 61, 193-216.
(11) Burgess, K. B.; Lim, D.; Martinez, C. I. Angew. Chem., Int. Ed.
Engl. 1996, 35, 1077-1078.
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7391-7394.
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Singh, G. P. J . Chem. Soc., Chem. Commun. 1994, 439-440. (b)
Beugelmans, R.; Singh, G. P.; Bois-Choussy, M.; Chastanet, J .; Zhu,
J . J . Org. Chem. 1994, 59, 5535-5542. (c) Zhu, J .; Bouillon, J . P.; Singh,
G. P.; Chastanet, J .; Beugelmans, R. Tetrahedron Lett. 1995, 36, 7081-
7084.
(14) (a) Beugelmans, R.; Bourdet, S.; Zhu, J . Tetrahedron Lett. 1995,
36, 1279-1282. (b) Zhu, J .; Beugelmans, R.; Bourdet, S.; Chastanet,
J .; Roussi, G. J . Org. Chem. 1995, 60, 6389-6396.
(15) Beugelmans, R.; Bigot, A.; Bois-Choussy, M.; Zhu, J . J . Org.
Chem. 1996, 61, 771-774.
(19) Evans, D. A.; Watson, P. S. Tetrahedron Lett. 1996, 37, 3251-
3254.
(20) Preliminary results concerning the synthesis of 3 and 4 have
been published: (a) Bois-Choussy, M.; Beugelmans, R.; Bouillon, J .
P.; Zhu, J . Tetrahedron Lett. 1995, 36, 4781-4784. (b) Beugelmans,
R.; Neuville, L.; Bois-Choussy, M.; Zhu, J . Tetrahedron Lett. 1995, 36,
8787-8790. The M configuration of the atropstereocenter for these
macrocycles has been erroneously assigned.
(16) (a) Rama Rao, A. V.; Reddy, K. L.; Rao, A. S. Tetrahedron Lett.
1994, 35, 8465-8468. (b) Rama Rao, A. V.; Reddy, K. L.; Rao, A. S.;
Vittal, T. V. S. K.; Reddy, M. M.; Pathi, P. L. Tetrahedron Lett. 1996,
37, 3023-3026.
(17) (a) Boger, D. L.; Borzilleri, R. M. Bioorg. Med. Chem. Lett. 1995,
5, 1187-1190. (b) Boger, D. L.; Borzilleri, R. M.; Nukui, S. Bioorg. Med.
Chem. Lett. 1995, 5, 3091-3096. (c) Boger, D. L.; Zhou, J .; Borzilleri,
R. M.; Nukui, S. Bioorg. Med. Chem. Lett. 1996, 6, 1089-1092. (c)
Boger, D. L.; Zhou, J . J . Org. Chem. 1996, 61, 3938-3939.
(18) (a) J anetka, J . W.; Rich, D. H. J . Am. Chem. Soc. 1995, 117,
10585-10586. (b) Pearson, A. J .; Bignan, G.; Zhang, P.; Chelliah, M.
J . Org. Chem. 1996, 61, 3940-3941. (c) Kra¨mer, R. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1197-1199.
(21) Albert, J . S.; Hamilton, A. D. Tetrahedron Lett. 1993, 34, 7363-
7366.
(22) (a) Evans, D. A.; Britton, T. C.; Ellman, J . A.; Dorow, R. L. J .
Am. Chem. Soc. 1990, 112, 4011-4030. (b) Evans, D. A.; Evrard, D.
A.; Rychnovsky, S. D.; Fru¨h, T.; Whittingham, W. G.; Devries, K. M.
Tetrahedron Lett. 1992, 33, 1189-1192.
(23) Maiti, S. N.; Singh, M. P.; Micetich, R. G. Tetrahedron Lett.
1986, 27, 1423-1424.

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9311
Sch em e 1
Sch em e 3
Sch em e 4
Sch em e 2
(LiOH, H2O2) to give benzoic acid which was also isolated
as the methyl ester 18.24 While no detailed mechanistic
studies have been carried out, a reaction scenario was
proposed as shown in Scheme 3. Enol A is formed
followed by nitrogen extrusion to give the imino ketone
B which was then hydrolyzed to R-keto acid C and
ultimately, to the benzoic acid D. This mechanism was
reminiscent of that of N-haloamino acid whose decom-
position mechanism has been investigated in detail.25 To
the best of our knowledge, such a decomposition pathway
has not yet been reported though R-azido acids are
common synthetic intermediates. While the above-
mentioned instability of R-azido acid may not be general,
degradation of several other R-aryl-R-azido acids has
indeed been observed in our laboratory.26
A more direct route for converting 12 into 16 is shown
in Scheme 4. Reductive removal of chiral oxazolidinone
27
with LiBH4 gave the corresponding alcohol 19, which
was transformed into 16 by way of straightforward
reduction-protection steps.
(R)-4-Fluoro-3-nitrophenylalanine (23) was synthesized
using Scho¨llkopf’s bislactim ether28 as chiral glycine
template under conditions that we have developed in
related studies15 (Scheme 5). Thus the higher order
(H.O.) organocuprate of 21 reacted with 4-fluoro-3-nitro-
benzyl bromide at -78 °C to afford the coupling product
22 in 90% yield. At 0 °C, some dialkylated product was
29
observed. Mixed H.O. organocuprate R(2-Th)CuCNLi2
could also be used to afford compound 22, albeit in
moderate yield. Mild acidic hydrolysis of 22 (TFA in
CH3CN) afforded the desired (R)-amino ester (23, 87%)
(24) While this control experiment did show the instability of R-azido
acid under hydrolytic conditions (LiOH and H2O2 in THF-H2O), it is
also possible, as suggested by a referee that byproduct 18 could directly
result from compound 12 before hydrolysis.
(25) Armesto, X. L.; Canle, M.; Losada, M.; Santaballa, J . A. J . Org.
Chem. 1994, 59, 4659-4664 and references cited therein.
(26) Decomposition was observed during the hydrolysis of 34 and
(4R)-3-[2-[3,5-bis(isopropyloxy)-4-methoxyphenyl]-1-oxoethyl]-4-
(phenylmethyl)-2-oxazolidinone.
of 15 into TBS-protected amino alcohol 16 was realized
uneventfully via a two-step sequence.
3-(Allyloxy)benzoic acid, isolated as the methyl ester
18 after CH2N2 treatment, was also formed in the
hydrolysis of 12. A control experiment showed that 18
resulted from the decomposition of the corresponding
R-azido acid 13. Thus, pure 13 obtained by flash chro-
matography was decomposed under hydrolytic conditions
(27) Penning, T. D.; Djuric, S. W.; Haack, R. A.; Kalish, V. J .;
Miyashiro, J . M.; Rowell, B. W.; Yu, S. S. Synth. Commun. 1990, 20,
307-312.
(28) Scho¨llkopf, U.; Groth, U.; Deng, C. Angew. Chem., Int. Ed. Engl.
1981, 20, 798-799.
(29) Lipshutz, B. H.; Koerner, M.; Parker, D. A. Tetrahedron Lett.
1987, 28, 945-948.

9312 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
Sch em e 5
Sch em e 6
which was coupled with D-(R)-N-Boc-N-methylleucine to
provide the dipeptide 25 in 93% yield. Hydrolysis of the
methyl ester gave the acid 26 in quantitative yield.
With the desired amino acids in hand, the synthesis
of the 16-membered macrocycle 3 was accomplished as
shown in Scheme 6. Coupling of 16 with L-(S)-N-alloc-
alanine 27 produced dipeptide 28 in 84% yield. Simul-
taneous reductive deprotection of O-allyl and N-alloc
groups using the reagent combination LiBH4-Pd(PPh3)4
(catalytic) recently developed in our laboratory30 fur-
nished the corresponding amino alcohol 29. The use of
LiBH4 was essential as other nucleophilic reagents such
as NaBH4 and amines led to a significant amount of
N-allylated product. The crude amino alcohol 29 thus
obtained was directly coupled with the dipeptide 26
(DPPA,31 DMF, Et3N)32 to give tetrapeptide 30 in 55%
overall yield. Little, if any, epimerization occurred in this
reaction. However, if EDC or DCC was employed as
coupling agent instead of DPPA, racemization at the
chiral center of amino ester 23 was observed, leading to
two separable diastereoisomers in a 2/1 ratio.
not fully stable. To our satisfaction, macrocyclization of
30 proceeded smoothly using anhydrous CsF in dry DMF
(0.01 M) at rt.14 Under these conditions, deprotection of
the primary alcohol and cyclization occurred in one pot
to afford the 16-membered macrocycle 31 as a single
isolable atropisomer in 63% yield. The newly created
chirality resulting from the restricted rotation of the
biaryl ether bond was determined by NOE techniques
(vide infra) to have a P configuration (helix nomencla-
ture)33 as shown in Scheme 6.
A major concern at the outset of these cyclization
studies was participation of the primary hydroxy group
as a potential nucleophile. In principle, two side reac-
tions were possible: (i) an intramolecular acyl transfer
reaction leading to a depsipeptide; (ii) nucleophilic attack
of the fluoro nitro aromatic system by the hydroxy group
leading to a 14-membered macrocycle via formation of
an aryl-alkyl ether bond. A carefully controlled experi-
ment showed that, under the above mentioned cyclization
conditions, deprotection of the TBS ether proceeds before
Treatment of a DMF solution of 30 with 6 equiv of
K2CO3 at room temperature did furnish the cyclized
product 31 but the conversion was low and longer
reaction time led to degradation, indicating that 30 was
(30) (a) Beugelmans, R.; Bourdet, S.; Bigot, A.; Zhu, J . Tetrahedron
Lett. 1994, 35, 4349-4350. (b) Beugelmans, R.; Neuville, L.; Bois-
Choussy, M.; Chastanet, J .; Zhu, J . Tetrahedron Lett. 1995, 36, 3129-
3132.
(31) Abbreviations used: DPPA, diphenylphosporyl azide; TFA,
trifluoroacetic acid; DCC, 1,3-dicyclohexylcarbodiimide; EDC, 1-[3-
(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride; HOBt, 1-hy-
droxybenzotriazole hydrate.
(33) The configuration (P or M) of the atropisomer was determined
by viewing the atropisomer as helix: “For this designation, only the
ligands of highest priority in front and in the back of the framework
are considered. If the turn from the priority front ligand to the priority
rear ligand is clockwise, the configuration is P, if counterclockwise it
is M”. See: Eliel, E. L.; Willen, S. H. Stereochemistry of Organic
Compounds; J ohn Wiley & Sons Inc.: New York, 1994; Chapter 14.
(32) Shioiri, T.; Ninomiya, K.; Yamada, S.-I. J . Am. Chem. Soc. 1972,
94, 6203-6205.

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9313
Sch em e 7
the cyclization. However, neither of these two side
reactions was observed.
Finally, removal of the Boc protective group of 31 was
carried out with 0.1 N HCl in CH3CN and after the usual
acid-base extraction, an analytically pure compound was
obtained whose physical data were in complete agree-
ment with those of the target structure. However, an
interesting phenomenon was observed during the course
F igu r e 3.
conditions afforded a 78% yield of diastereomerically pure
34 which, in the presence of Boc anhydride, was treated
with hydrogen over 10% palladium on carbon to give 35.35
Hydrolysis of the latter with LiOH furnished the desired
amino acid (S)-32 in quantitative yield.
1
of NMR studies. Well-resolved H NMR spectra of this
compound (named 3′) could be obtained both in CDCl3
and in freshly prepared Me2CO-d6 solution at room
temperature. Curiously, in Me2CO-d6, the intensity of
the initial set of resonances (3′) decreased and a second
set of resonances (named 3) appeared over a period of
several hours. After 12 h at room temperature, the ratio
of 3/3′ became 1/1. Pure 3 could be produced by heating
an acetone solution of 3′ at 60 °C for 30 min or even at 0
°C over a period of 1 week.
The sufficient stability of 3′ in CDCl3 allowed detailed
NMR studies. Both 3 and 3′ had an intense NOE
crosspeak in NOESY spectra between H-20 and H-14
indicative of P configuration at the atropstereocenter;
hence they are not atropisomers. As epimerization of the
peptide backbone in acetone solution seems improbable,
this observation could be tentatively explained in terms
of conformational changes or different aggregation states.
It is worth noting that compound 3′ had negative NOE
effects at 268 K, unusual for such a small molecular
weight compound (MW ) 541) and in such a nonviscous
solvent as CHCl3. This is indicative of aggregates.34 In
addition, several NOE cross peaks could only be ex-
plained by means of self-association of the molecule, e.g.
the NOEs between H-22 and NH-23, NH-9 and N-MeH,
which may be diagnostic of head-to-tail dimer of 3. The
1H NMR and IR spectra of 3′ are concentration dependent
which is also consistent with the suggested aggregation.
No further efforts have been devoted to defining the exact
conformational properties of 3′ and in the following
discussion, compound 3 refers to the conformer produced
after acetone treatment.
For the synthesis of 4, two strategies could be envis-
aged (Figure 3). The first one, involving a one-pot double
intramolecular SNAr reaction of a linear tetrapeptide A,
has been successful in the synthesis of the bicyclic C-O-
D-O-E ring of vancomycin;36 the second one involves
sequential SNAr reactions via the monocyclic intermedi-
ate B. Although it would be interesting to see the
outcome of the cyclization of substrate A (whether bicyclic
16+14 or 17+13 pathway), the second strategy was
preferred for the purpose of differentiating the two nitro
groups. Synthesis of the linear tripeptide 40 was achieved
as follows (Scheme 8). Coupling of the amino alcohol 16
with the racemization-prone L-(S)-N-Boc-[3-(isopropyl-
oxy)phenyl]glycine (32) (EDC, HOBt) provided the dipep-
tide 36 in 92% yield. The presence of HOBt is essential
to minimize racemization and other coupling conditions,
37
including EDC-CuCl2 or DPPA, did not give superior
results in terms of diastereomeric purity. Palladium-
catalyzed reductive removal of the allyl protecting group30
afforded compound 37 in 85% yield with less than 5%
racemization as determined by NMR analysis. Applica-
tion of the TBDMSOTf-mediated one step deprotection-
protection procedure38 to 37 provided 38. This amine was
coupled with D-(R)-N-Boc-4-fluoro-3-nitrophenylalanine
(39), in turn obtained from 23 via amine protection (Boc)
and ester hydrolysis, to furnish the tripeptide 40 in
excellent yield. The small amount of undesired diaste-
reoisomer was readily removed by flash chromatography.
Macrocyclization of diastereomerically pure 40 using
dry CsF as promotor in DMF (0.01M) gave an 84% yield
Syn th esis of th e Bicyclic D-O-E-F -O-G Rin g of
Teicop la n in 4. To proceed to the synthesis of 4, another
nonproteinogenic amino acid, L-(S)-N-Boc-[3-(isopropyl-
oxy)phenyl]glycine (32), was required. Evans’ asym-
metric azidation method once again proved to be very
efficient (Scheme 7). Azidation of 33 under standard
(35) Saito, S.; Nakajima, H.; Inaba, M.; Moriwake, T. Tetrahedron
Lett. 1989, 30, 837-838.
(36) Beugelmans, R.; Bois-Choussy, M.; Vergne, C.; Bouillon, J . P.;
Zhu, J . J . Chem. Soc., Chem. Commun. 1996, 1029-1030.
(37) Miyazawa, T.; Otomatsu, T.; Fukui, Y.; Yamada, T.; Kuwata,
S. Int. J . Peptide Protein Res. 1992, 39, 237-244.
(34) For a brief discussion concerning negative NOE effects, see ref
1a.
(38) Sakaitani, M.; Ohfune, Y. J . Org. Chem. 1990, 55, 870-876.

9314 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
Sch em e 8
Sch em e 9
Sch em e 10
of the desired macrocyclic D-O-E ring (41) as a single
atropisomer with the “nonnatural” (P) configuration. To
ascertain the absence of racemization in this key ring
closure step, racemic amino acid (()-32 was prepared via
a Strecker synthesis39 and incorporated into the tripep-
tide 40 following the previously described synthetic
scheme. Flash chromatographic separation then gave the
diastereomerically pure compounds 40 (R,S,R) and epi-
40 (R,R,R). Cyclization of the latter under conditions
identical to that used for 40 afforded the epi-41 macro-
cycle (Scheme 9) which had an Rf value and physical data
completely different from those of 41. This result con-
vincingly showed that no racemization had occurred
under our macrocyclization conditions. Similar observa-
tions have recently been disclosed in related cyclization
19
studies carried out by Boger’s17b and Evans’ groups. It
is interesting to note that CsF40 played a dual role in this
cyclization reaction: it removed the TBS protecting group
and promoted the cyclization in a one-pot fashion.
The completion of the synthesis of the bicyclic D-O-E-
F -O-G ring model 4 is shown in Scheme 10. Cleavage of
the Boc group and the isopropyl ether was realized in a
single step by treatment of 41 with BCl3 followed by
acidic workup and simple acid-base extraction, providing
pure amino compound 42 in 73% yield. DPPA-promoted
coupling between 42 and the known (3-fluoro-4-nitro-
phenyl)acetic acid (43)14 gave the desired macrocycliza-
tion precursor 44 in 94% yield. This reaction is note-
worthy in that the two hydroxy groups do not need to be
protected. After studying different reaction parameters,
the optimized conditions for the cyclization of 44, leading
to the bicyclic D-O-E-F -O-G ring compound 4 in 87%
yield, were found to be 10 equiv of K2CO3 in THF in the
presence of crown ether (18-C-6).41 Given the obvious
strain in this bicyclic system, the high yield and mild
(39) (a) Mai, K.; Patil, G. Org. Prep. Proced. Int. 1985, 17, 183-
186. (b) Zhu, J .; Beugelmans, R.; Bigot, R.; Singh, G. P.; Bois-Choussy,
M. Tetrahedron Lett. 1993, 34, 7401-7404.
(40) Clark J . H. Chem. Rev. 1980, 80, 429-452.

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9315
Ta ble 1. 1H NMR Assign m en t of 3 a n d NOE Obser ved
(CD3CN, 300 K)
Sch em e 11
proton
H17
H20
NH9
H5
chemical shift
NOE
7.90, d
7.75, dd
7.31, d
7.29, t
H15
H15′, H14, H21, H19
H22, H11, H8, H21, NH12
H4, H6
H6
H19
NH12
H4
H21
H8
H11
H14
H15′
H22
7.10, dd
6.99, d
6.95, d
6.91, DD
6.18, t
4.76, td
4.45, qd
4.33, dd
3.59, dd
3.46, d
3.27, dd
3.18, dd
2.40 s
1.65 m
1.35 m
1.25, d
0.95 m
0.88, d
0.86, d
H5
H20
NH9, H8, H11, H14, MeAla
H5
H22, H8, NH9
H21, H22, NH9, NH12
NH9, NH12, MeAla
H20, NH12, N15′, H15
H20, H14, H15
NH9, H21, H8
H17, H14, H15′
H15
H25
N-Me
H26′
H26
CH3(Ala)
H27
H11, NH12
H-20 and H-15′, and more importantly between H-20 and
H-14. No NOE was observed between H-17 and H-14,
thus eliminating the possibility of an M configuration for
the atropstereocenter. Full assignments of the spectra
of 41 and 4 were made in an entirely analogous way. The
atropstereoisomerism of compound 41 was determined
by spectra recorded in MeCN-d3 at 313 K. Once again,
the NOE crosspeak between H-20 and H-14 was highly
indicative of a P configuration for the atropstereocenter.
A conformational search of compound 3 revealed that for
the atropisomer with P configuration, the distance be-
tween H-14 and H-20 is 2.71 Å, while that between H-14
and H-17 is 4.39 Å. Similarly, for the M configuration,
the distances between H-14 and H-20, and between H-14
and H-17 were found to be 4.38 and 2.72 Å, respectively.
These computational results are in full agreement with
our NOE observations.
In the course of these studies, we observed an interest-
ing conformational property of compounds 3 and 41.
From Williams’ classic studies of the vancomycin struc-
ture, it is known that the carboxylate binding pocket of
the antibiotic is formed only in the presence of the cell
wall peptide. In its absence, three amide protons, NH-
9, NH-12, and NH-23, were oriented alternately up-
down-up, a usual arrangement found in the normal
â-pleated sheet form. Significantly, NOE crosspeaks
between NH-12 and NH-9 for compound 3 and between
NH-12, NH-9, NHBoc, and H-17 for compound 41 were
found in both acetone and acetonitrile solution. These
observations established that NH-12 of Ala had rotated
from its “normal” position at the “back” of the molecule
to the “front” face of the structure and that the conformer
needed to bind the same carboxylate function was
significantly populated in both solvents. The low energy
requirement for pocket formation in compound 3 and 41
could derive from the fact that the amino acids have the
R, R, S, and R configuration at positions 1, 2, 3, and 4
from the N-terminus.
CH3(Leu)
CH3(Leu)
conditions of this second macrocyclization are remark-
able. The bicyclic D-O-E-F -O-G ring model, obtained in
28% overall yield from the first peptide coupling reac-
tion, is the most advanced synthetic intermediate to
date for the total synthesis of teicoplanin and related
antibiotics.
Ster eoch em istr y of Atr op d ia ster eoisom er s a n d
Con for m a tion a l Stu d ies. Due to restricted rotation of
the biaryl ether bond across the 16-membered macrocycle
and on the basis of our previous synthesis of model C-O-D
rings,13 formation of two atropisomers may be anticipated
in the cyclization of compounds 30 and 40. Much to our
surprise, cyclization of 30 or 40 gave the corresponding
cyclic compounds 31 or 41, respectively, as single isolable
atropisomers. The configuration of the newly formed
chiral atropstereocenter was determined from detailed
NMR analysis of the final compound 3. Initial studies
were carried out in Me2CO-d6 solution, and although the
resolution was good, the overlap of H-14 and H-11 proton
signals made the stereochemical assignment difficult.
After screening of conventional deuterated solvents, we
found that MeCN-d3 was the best choice for our purpose.
In this solvent, both 3 and 41 adopt a single conformation
1
and the H NMR signals could be fully assigned from 2D
1H-1H COSY 90, NOEDIFF, and 2D NOESY experi-
ments. The 1H NMR assignments and NOE effects
observed for compound 3 are listed in Table 1.
The easy identification of H-17 (downfield) ortho to the
nitro function allowed assignment of H-20, and subse-
quently of H-19; while the proton H-21, whose shift to
high field is characteristic of a cyclic structure, led to the
localization of H-4, H-5, and H-6. The methyl protons of
alanine, which showed a distinct doublet at δ ) 1.25 ppm
(d, J ) 7.2 Hz), served to assign H-11, and hence NH-
12. The NH-9 resonance was established from its
coupling with H-8 which, in turn is coupled to the two
H-22 protons. Through these iterative COSY and NOE-
SY studies, all the protons were thus unambiguously
located. An intense NOE, characteristic of a P configu-
ration for the atropstereocenter, was observed between
The high atropdiastereoselectivity observed in the
formation of 3 and 41 is unique. To determine if the
presence of the primary hydroxy function may play a role
(e.g. via hydrogen bonding with the nitro group) in the
stereoselective ring formation, compounds 45a and 45b
were prepared. Cyclization of 45a and 45b under the
standard conditions (CsF, DMF) again gave single atro-
pisomers 46a and 46b, respectively, in 75% yield (Scheme
11). This control experiment shows that the primary
(41) The following conditions have also been tested for closing the
14-membered ring: CsF-DMF, K2CO3-DMF, K2CO3-THF, K2CO3-
MeCN, K2CO3-DMSO. None of these gave satisfactory results.

9316 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
toward those of the complexed form. The molar fraction
(X) of free substrate 3 in the equilibrium mixture can be
expressed as shown in eq 1 where ∆δmax ) δb - δf, ∆δobs
) δobs - δf
X ) 1 - (∆δobs/∆δmax
)
(1)
The dissociation constant Kd can be expressed by eq 2
where [S]0 is the initial concentration of 3 and [R]0 is the
initial concentration of AcLact:
Kd ) X [[R]0 - (1 - X) [S]0]/1 - X
(2)
The chemical shift change of NH-12 was subjected to
a curve fitting method.43 In connection with the above
relationship (eq 2), a dissociation constant (Kd) of 5 × 10-4
between 3 and Ac-D-lactate has been determined. About
83% of 3 was present in the bound form when 1.05 equiv
of Ac-D-lactate was added. This value compares favorably
to the binding between vancomycin and Ac-D-Ala where
only 69% of the antibiotic was in the complexed form at
the highest concentration of Ac-D-Ala.44
F igu r e 4.
1
The proton assignment of bound 3 was made by a H-
hydroxy group is not responsible for the observed atro-
1H COSY technique. It was seen that almost all the
protons of compound 3 were influenced by the binding.
A surprising observation was that the chemical shift of
NH-9 was almost unchanged upon addition of AcLact.
One possible explanation for this is a relatively strong
internal hydrogen bonding between the primary hydroxyl
group and NH-9 which may have some inhibitory effect
on its binding with AcLact.45 Besides the amide protons,
large opposing shielding effects were observed for H-15
methylene protons. Thus, one was shifted to low field
(∆δ ) +103 Hz) and the other to high field (∆δ ) -83
Hz). Another major perturbation after addition of Ac-D-
lactic acid involved the H-20 proton (from 7.78 to 7.71
ppm) which was shifted downfield relative to H-17 (from
7.67 to 7.75 ppm). Similar opposed shielding effects of
H-17 (upfield) and H-20 (downfield) have been observed
upon complex formation between vancomycin and Ac-D-
Ala-D-Ala.44 The slight modification of the relative posi-
tion of the two aromatic rings D and E may account for
such changes. It is also clear from the values of J R,NH
(9.0 Hz for free substrate and 9.62 Hz for the bound form)
that no major conformational change such as peptide
bond rotation or cis-trans isomerization takes place on
binding. The conformation of 3 in its bound state might
be essentially the same as in its free state. Unfortu-
nately, the failure to identify the NH-23 amide proton
in the NMR despite the use of different solvents has thus
far hampered the definition of the exact structure of the
complex.
pstereoselectivity in the cyclization of 30 and 40.
Boger et al.17b and Evans et al.19 have very recently
carried out the cyclization of 47 and 48 (Figure 4) and
have reported the formation of the two possible atropi-
somers with a slight preference for the nonnatural one
(P configuration). Intrigued by these subtle differences
in terms of atropdiastereoselectivity, we carried out a
detailed computational study of compounds 30 and 47.
While the result is indeed in agreement with the pref-
erential formation of the P configuration,42 we found that
the difference in conformational properties between 30
and 47 is not significant enough to account for the higher
atropdiastereoselectivity of 30 vs 47. Further studies are
in progress to understand the intrinsic atropdiastereo-
selectivity observed in the above-mentioned cyclization.
Bin d in g Stu d ies. The initial motivation in synthe-
sizing compounds 3 and 4 was to enhance the affinity
with Ac-D-Ala-D-lactate by means of the primary hydroxy
group. The binding properties of 3 with Ac-D-Lact were
studied by 1H NMR titration experiments. Because there
is a rapid exchange between the free and bound species,
the observed chemical shifts are weighted averages of the
free (δf) and bound (δb) species under conditions of fast
exchange on the NMR time scale. As the amount of
AcLact is increased, the signals of 3 shift progressively
(42) Five thousand conformations of the precursor 45a and macro-
cyclic product 46a were generated by a random search Monte Carlo
method and optimized by molecular mechanics minimization using the
Macromodel (Version 3.5) program with the AMBER hydrocarbon force
field. From these 5000 conformations, only the conformations with
energy values within 3.0 kcal/mol compared to the most stable
conformation were analyzed. AMBER generated geometries served as
starting points for calculating heats of formation with the help of the
MOPAC program (Version 5.0) using semiempirical AM1/RHF param-
eters (Dewar, M. J . S.; Zoebisch, E. G.; Healy, E. F.; Stewart, J . P. J .
Am. Chem. Soc. 1985, 107, 3902-3909). The AM1 calculated heats of
formation of the two lowest energy conformers 45a -P (P configuration)-
and 45a -M (M configuration) which have very similar geometrical
features to those of the two atropisomers 46a -P (P configuration) and
46a -M (M configuration) were found to be -244.04 and -241.42 kcal/
mol, respectively. The torsional angles around the C14-C15 and C15-
C16 bonds of 45a -P are -73°52 and -76°35 while those of 45a -M are
-49°17 and -62°27, respectively. The reduced torsional angles found
in the latter create severe steric interactions in the E ring between
the methyl hydrogen of the Ala moiety and C19 and between NH12
and C17. These unfavorable interactions may explain the greater heat
of formation of 45a -M compared to 45a -P and suggest the predominant
formation of 46a -P .
Interesting biological properties of compounds 3′, 3,
and 4 were observed and will be detailed elsewhere.
Con clu sion
We have described an efficient synthesis of modified
binding pockets of vancomycin and teicoplanin (3 and 4),
employing a unique SNAr-based macrocyclization tech-
nique under conditions sufficiently mild that the config-
uration of the racemization-prone arylglycine is not
(43) Wilcox, C. S.; Cowart, M. D. Tetrahedron Lett. 1986, 27, 5563-
5566.
(44) Convert, O.; Bongini, A.; Feeney, J . J . Chem. Soc., Perkin Trans.
2 1980, 1262-1270.
(45) Adrian, J . C.; Wilcox, C. S. J . Am. Chem. Soc. 1992, 114, 1398-
1403.

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9317
Hz, 1H), 4.20 (m, 4H), 4.51 (septet, J ) 6.0 Hz, 1H), 4.65 (m,
1H), 6.8-7.3 (m, 9H); 13C NMR (CDCl3) δ 22.0, 37.6, 41.5, 55.2,
66.0, 69.7, 114.6, 117.3, 121.8, 127.2, 128.9, 129.4, 129.5, 135.0,
135.1, 153.3, 158.0, 171.0; MS m/ z 354 (M + H+). Anal. Calcd
for C21H23NO4: C, 71.37; H, 6.56; N, 3.96. Found: C, 70.88;
H, 6.67; N, 3.97.
affected. The synthesis of 4 represents the most ad-
vanced synthetic intermediate toward the total synthesis
of teicoplanin. The facile cyclization observed in the
synthesis of this highly constrained 16+14 bicyclic com-
pound is remarkable and illustrates the power of the
intramolecular SNAr reaction for the construction of
complex molecular frameworks. Further studies toward
designing more elaborate models of modified vancomycin
binding pocket as well as toward the total synthesis of
natural products are being actively pursued.
(2R,4R)-3-[2-Azid o-2-[3-(a llyloxy)p h en yl]-1-oxoeth yl]-
4-(p h en ylm eth yl)-2-oxa zolid in on e (12). To the solution of
KHMDS (37 mL, 0.5 M, 18.5 mmol) in dry THF (40 mL),
stirred at -78 °C under argon, was added via syringe a
precooled (-78 °C) solution of imide 11 (5.4 g, 15.4 mmol) in
dry THF (90 mL). The resulting yellow solution was stirred
at -78 °C for 30 min, and then a precooled (-78 °C) solution
of trisyl azide (5.71 g, 18.5 mmol) in dry THF (50 mL) was
introduced via syringe. The reaction was stirred for 4 min at
-78 °C (the solution became slightly red) and was then
quenched by addition of HOAc (4.4 mL, 76.9 mmol). The
cooling bath was removed, and the reaction mixture was
stirred at rt for 90 min. Saturated aqueous NH4Cl (50 mL)
was added, and the aqueous layer was extracted with EtOAc.
The organic phase was washed with brine, dried (Na2SO4), and
evaporated. To the above-obtained reaction mixture in acetone
(250 mL), NaI (11.5 g, 77.0 mmol) and NaOAc‚3H2O (6.3 g,
46.1 mmol) were added and stirring was continued for 3 h at
room temperature. Inorganic salt was removed by filtration.
The filtrate was evaporated and then partitioned between
CH2Cl2 and H2O. The aqueous phase was extracted with CH2-
Cl2. The combined organic phases were washed with brine,
dried (Na2SO4), and evaporated in vacuo. The crude product
was purified by flash chromatography (SiO2, EtOAc/heptane
) 1/6) to give the major diastereoisomer 12 (4.95 g, 82%) as
colorless oil: [R]D -201.5° (c 4.1, CHCl3); IR (CHCl3) 2110,
Exp er im en ta l P r oced u r e
General procedures and methods for characterization have
been described previously.13b Melting points are uncorrected.
[3-(Allyloxy)p h en yl]a cetic Acid (9). To a solution of (3-
hydroxyphenyl)acetic acid (8, 5.0 g, 32.9 mmol) in THF (500
mL) was added NaH (3.95 g, 98.7 mmol). After 1 h of stirring
allyl bromide (11.4 mL, 131.6 mmol) was added, and the
resulting reaction mixture was heated to reflux for 15 h. The
reaction was cooled to 0 °C, quenched by addition of water,
and stirred for 2 h at room temperature. The volatile was
evaporated, and the residue was extracted with ether to
remove the neutral species. The aqueous phase was then
acidified and extracted with dichloromethane. The combined
organic phases were washed with brine, dried over Na2SO4,
and evaporated to give a white solid. Recrystallization from
ether-heptane gave 9 as white needles (6.2 g, 98%): mp 78
°C; IR (CHCl3) 3300, 1716, 1580 cm-1 1H NMR (200 MHz,
;
CDCl3) δ 3.61 (s, 2H), 4.52 (dt, J ) 1.5, 5.3 Hz, 2H), 5.23 (qd,
J ) 1.5, 10.6 Hz, 1H), 5.39 (qd, J ) 1.5, 17.3 Hz, 1H), 6.03
(tdd, J ) 5.3, 10.6, 17.3 Hz, 1H), 6.80 (m, 2H), 7.20 (m, 2H);
13C NMR (CDCl3) δ 41.9, 69.6, 114.5, 116.8, 118.5, 122.7, 130.4,
134.0, 135.5, 159.6, 178.8; MS m/ z 192. Anal. Calcd for
C11H12O3: C, 68.73; H, 6.29. Found: C, 68.71; H, 6.24.
(4R)-3-[2-[3-(Allyloxy)p h en yl]-1-oxoet h yl]-4-(p h en yl-
m eth yl)-2-oxa zolid in on e (11). A solution of [3-(allyloxy)-
phenyl]acetic acid (9,1.92 g, 10 mmol) in dry THF (40 mL) was
cooled to -78 °C, and Et3N (1.68 mL, 12 mmol) and redistilled
pivaloyl chloride (1.29 mL, 10.5 mmol) were added successively
via syringe with stirring. The resulting slurry was stirred at
-78 °C for 15 min and at 0 °C for 45 min and then cooled
again to -78 °C. In a separate flask, (4R)-4-(phenylmethyl)-
2-oxazolidinone (2.12 g, 12 mmol) was dissolved in dry THF
(40 mL) and cooled to -78 °C, a solution of butyllithium in
hexane (7.5 mL, 1.6 M) was added slowly and stirred at -78
°C for another 5 min after completion of the addition. The
so-formed metalated oxazolidinone (yellow colored) was trans-
fered via cannula to the flask containing the mixed anhydride.
The resulting slurry was stirred for 15 min at -78 °C and then
warmed up to room temperature over 90 min. The reaction
was quenched by addition of aqueous NH4Cl, the volatile was
removed in vacuo, and the aqueous solution was extracted with
EtOAc. The combined organic phases were washed with brine,
dried (Na2SO4), and evaporated in vacuo. The crude product
was purified by flash chromatography (SiO2, EtOAc/heptane
) 1/6 then 1/3) to afford compound 11 as a colorless oil (2.81
g, 80%): [R]D -104° (c 2, CHCl3); IR (CHCl3) 1780, 1700, 1386,
1785, 1706, 1387, 1368 cm-1 1H NMR (200 MHz, CDCl3) δ
;
2.86 (dd, J ) 9.6, 13.3 Hz, 1H), 3.40 (dd, J ) 3.2, 13.3 Hz,
1H), 4.08-4.20 (m, 2H), 4.52 (td, J ) 1.5, 5.3 Hz, 2H), 4.65
(tdd, J ) 3.2, 7.4 and 9.6 Hz, 1H), 5.28 (qd, J ) 1.5, 10.4 Hz,
1H), 5.42 (qd, J ) 1.5, 17.3 Hz, 1H), 6.05 (tdd, J ) 5.3, 10.4
and 17.3 Hz, 1H), 6.30 (s, 1H), 6.9-7.4 (m, 9H); 13C NMR
(CDCl3) δ 37.8, 55.8, 63.7, 66.6, 69.1, 115.0, 116.2, 117.9, 121.0,
123.7, 127.7, 129.1, 129.5, 130.2, 133.1, 134.4, 134.9, 152.5,
159.2, 169.4; MS m/ z 392, 364, 351. Anal. Calcd for
C21H20N4O4: C, 64.28; H, 5.14; N, 14.28. Found: C, 63.63; H,
5.15; N, 13.83. Minor diastereoisomer: mp 110-112 °C; [R]D
+83.3° (c 0.72, CHCl3); IR (CHCl3) 2110, 1784, 1707, 1387,
1368 cm-1 1H NMR (200 MHz, CDCl3) δ 2.63 (dd, J ) 9.1,
;
13.4 Hz, 1H), 3.40 (dd, J ) 3.4, 13.4 Hz, 1H), 4.12 (dd, J )
3.3, 9.1 Hz, 1H), 4.25 (t, J ) 9.1 Hz, 1H), 4.56 (td, J ) 1.4, 5.2
Hz, 2H), 4.78 (tt, J ) 3.4, 9.3 Hz, 1H), 5.27 (qd, J ) 1.4, 10.5
Hz, 1H), 5.41 (qd, J ) 1.4, 17.2 Hz, 1H), 6.05 (tdd, J ) 5.2,
10.4 and 17.2 Hz, 1H), 6.11 (s, 1H), 6.9-7.4 (m, 9H); 13C NMR
(CDCl3) δ 37.5, 55.1, 63.5, 66.6, 69.1, 115.1, 116.5, 117.9, 121.2,
127.6, 129.2, 129.5, 130.3, 133.1, 134.5, 134.6, 152.7, 159.4,
169.3; MS m/ z 392, 364, 351. Anal. Calcd for C21H20N4O4:
C, 64.28; H, 5.14; N, 14.28. Found: C, 63.93; H, 5.17; N, 13.96.
(2S,4S)-3-[2-Azid o-2-[3-(isop r op yloxy)p h en yl]-1-oxoet-
h yl]-4-(p h en ylm eth yl)-2-oxa zolid in on e (34). Following the
procedure detailed for 12, compound 34 was isolated in 95%
yield: mp 87 °C; [R]D +210° (c 0.50, CHCl3); IR (CHCl3) 2987,
2106, 1781, 1712, 1600, 1387, 1368 cm-1; 1H NMR (250 MHz,
CDCl3) δ 1.33 (d, J ) 6.1 Hz, 6H), 2.85 (dd, J ) 9.7, 13.4 Hz,
1H), 3.41 (dd, J ) 3.2, 13.4 Hz, 1H), 4.1-4.2 (m, 2H), 4.55
(septet, J ) 6.1 Hz, 1H), 4.62 (m, 1H), 6.09 (s, 1H), 6.9-7.4
(m, 9H); 13C NMR (CDCl3) δ 21.9, 37.4, 55.5, 63.4, 66.3, 69.9,
115.7, 116.9, 120.3, 127.4, 128.9, 129.3, 130.0, 134.1, 134.8,
152.3, 158.3, 169.2; MS m/ z 366 (M - N2), 351. Anal. Calcd
for C21H22N4O4: C, 63.95; H, 5.62. Found: C, 64.13; H, 6.03.
(2R)-2-Azid o-2-[3-(a llyloxy)p h en yl][Acetic Acid Meth yl
Ester (14). To a solution of 12 (3.2 g, 8.1 mmol) in THF (120
mL) and H2O (40 mL) was added LiOH‚H2O (685 mg, 16. 32
mmol) and H2O2 (4.6 mL, 40.8 mmol) at 0 °C. The reaction
mixture was stirred for 3 h at 0 °C and the volatile was
evaporated. The residue was diluted with 20 mL of 0.5 N
aqueous NaHCO3 and extracted with ether. The combined
organic phase was washed with brine, dried (Na2SO4), and
evaporated to afford the recovered chiral auxiliary 10 (1.34 g,
93%). The aqueous phase was acidified to pH 1-2 with 3 N
1367 cm-1 1H NMR (200 MHz, CDCl3) δ 2.78 (dd, J ) 8.4,
;
13.4 Hz, 1H), 3.25 (dd, J ) 3.3, 13.4 Hz, 1H), 4.12-4.18 (m,
2H), 4.20 (d, J ) 15.4 Hz, 1H), 4.30 (d, J ) 15.4 Hz, 1H), 4.52
(td, J ) 1.5, 5.3 Hz, 2H), 4.66 (tdd, J ) 3.3, 7.1 and 13.4 Hz,
1H), 5.28 (qd, J ) 1.5, 10.5 Hz, 1H), 5.42 (qd, J ) 1.5, 17.3
Hz, 1H), 6.05 (tdd, J ) 5.3, 10.5 and 17.3 Hz, 1H), 6.8-7.3
(m, 9H); 13C NMR (CDCl3) δ 37.2, 41.1, 54.8, 65.7, 68.3, 113.2,
116.0, 117.1, 122.0, 126.9, 128.5, 129.2, 133.1, 134.9, 153.1,
158.5, 170.5; MS m/z 351, 174. Anal. Calcd for C21H21NO4:
C, 71.78; H, 6.02; N, 3.99. Found: C, 71.57; H, 6.07; N, 3.94.
(4S )-3-[2-[3-(I s o p r o p y lo x y )p h e n y l]-1-o x o e t h y l]-4-
(p h en ylm eth yl)-2-oxa zolid in on e (33). Following the pro-
cedure detailed for 11, compound 33 was isolated in 95%
yield: [R]D +51.3° (c 1.1, CHCl3); IR (CHCl3) 1780, 1695, 1595,
1
1460 cm-1; H NMR (200 MHz, CDCl3) δ 1.32 (d, J ) 6.0 Hz,
6H), 2.78 (dd, J ) 9.4, 13.4 Hz, 1H), 3.27 (dd, J ) 3.3, 13.4

9318 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
aqueous HCl and extracted with CH2Cl2. The combined
organic extracts were washed with brine, dried, and evapo-
rated to give the R-azido acid 13 (1.62 g, 85.2%) which was
directly esterified with diazomethane to afford the methyl
R-azido ester 14 in quantitative yield: IR (CHCl3) 2112, 1742
cm-1; 1H NMR (250 MHz, CDCl3) δ 3.78 (s, 3H), 4.55 (td, J )
1.5, 5.3 Hz, 2H), 4.97 (s, 1H), 5.29 (qd, J ) 1.5, 10.5 Hz, 1H),
5.43 (qd, J ) 1.5, 17.3 Hz, 1H), 6.05 (tdd, J ) 5.3, 10.5, 17.3
Hz, 1H), 6.9-7.4 (m, 4H); 13C NMR (CDCl3) δ 52.9, 65.4, 69.1,
114.2, 115.8, 117.9, 120.2, 130.2, 133.1, 135.4, 159.3, 169.5;
MS m/ z 247, 205, 188; HRMS m/ z 247.0953 (C12H13N3O3
requires 247.0957).
washed with brine, dried (Na2SO4), and evaporated in vacuo.
The crude product was purified by flash chromatography (SiO2,
EtOAc:heptane ) 1/3 then 1/2) to give compound 16 (311 mg,
89%) as a colorless oil: [R]D -10.7° (c 0.7, CHCl3); IR (CHCl3)
3300-3500, 2990, 1610, 1500 cm-1; 1H NMR (200 MHz, CDCl3)
δ -0.1 (s, 6H), 0.85 (s, 9H), 3.58 (dd, J ) 8.0, 10.1 Hz, 1H),
3.78 (dd, J ) 4.0, 10.1 Hz, 1H), 4.03 (dd, J ) 4.0, 8.0 Hz, 1H),
4.50 (td, J ) 1.5, 5.3 Hz, 2H), 5.24 (qd, J ) 1.5, 10.5 Hz, 1H),
5.39 (qd, J ) 1.5, 17.3 Hz, 1H), 6.01 (tdd, J ) 5.3, 10.5 and
17.3 Hz, 1H), 6.8-6.9 (m, 3H), 7.18 (t, J ) 7.5 Hz, 1H); 13C
NMR (CDCl3) δ -5.4, 18.4, 26.0, 57.6, 68.1, 69.0, 113.5, 114.5,
117.7, 119.6, 129.7, 133.4, 141.7, 159.0; MS m/ z 307, 250, 162.
Anal. Calcd for C17H29NO2Si: C, 66.40; H, 9.51; N, 4.55.
Found: C, 66.25; H, 9.37; N, 4.56.
D-2-Hyd r oxy-1-[3-(a llyloxy)p h en yl]eth yl Azid e (19). To
a solution of compound 12 (1.58g, 4.04 mmol) in Et2O (50 mL)
were added distilled water (218 µL, 12.10 mmol) and LiBH4
(267 mg, 12.10 mmol) at 0 °C. After being stirred for 1 h at 0
°C, the reaction mixture was quenched by addition of HCl (1
N). The aqueous phases (pH ) 4) were extracted with EtOAc.
The combined organic phases were washed with brine, dried
(Na2SO4), and evaporated in vacuo. The crude product was
purified by flash chromatography (SiO2, EtOAc/heptane ) 1/1)
to afford compound 19 (725 mg, 82%) as a colorless oil: [R]D
-158.6° (c 0.76, CHCl3); IR (CHCl3) 3480, 2933, 2115, 1611,
N-(L-2-Acet oxyp r op ion yl)-D-[3-(a llyloxy)p h en yl]gly-
cin e Meth yl Ester (17). A solution of 15 (72.0 mg, 0.33
mmol), (S)-2-(acetyloxy)propionyl chloride (118.5 µL, 1.02
mmol), DMAP (42 mg, 0.34 mmol) and Et3N (173 µL, 1.23
mmol) in CH2Cl2 was stirred at 0 °C for 1 h. The reaction
mixture was diluted with aqueous NH4Cl, and the aqueous
solution was extracted with CH2Cl2. The combined organic
extracts were washed with brine, dried (Na2SO4), and evapo-
rated. Flash chromatography (SiO2, EtOAc/heptane ) 1/2)
afforded amide 17 (106.0 mg, 96%): mp 84-85; [R]D -104.9°
(c 0.9, CHCl3); IR (CHCl3) 3431, 3025, 1738, 1694, 1606, 1513,
1
1580 cm-1; H NMR (200 MHz, CDCl3) δ 3.70 (m, 2H), 4.55
(td, J ) 1.4, 5.3 Hz, 2H), 4.65 (m, 1H), 5.30 (qd, J ) 1.4, 10.5
Hz, 1H), 5.42 (qd, J ) 1.4, 17.2 Hz, 1H), 6.10 (m, 1H), 6.90
(m, 3H), 7.3 (m, 1H); 13C NMR (CDCl3) δ 66.4, 67.7, 68.9, 113.7,
114.8, 117.9, 119.6, 130.0, 133.0, 137.9, 159.0; MS m/ z 219,
202, 187. Anal. Calcd for C11H13N3O2: C, 60.26; H, 5.98.
Found: C, 60.42; H, 6.26.
1
1431 cm-1; H NMR (200 MHz, CDCl3) δ 1.48 (d, J ) 6.8 Hz,
3H), 2.15 (s, 3H), 3.74 (s, 3H), 4.52 (dt, J ) 1.5, 5.3 Hz, 2H),
5.23 (q, J ) 6.8 Hz, 1H), 5.29 (qd, J ) 1.5, 10.4 Hz, 1H), 5.42
(qd, J ) 1.5, 17.2 Hz, 1H), 5.51 (d, J ) 7.1 Hz, 1H), 6.04 (tdd,
J ) 5.3, 10.4, 17.2 Hz, 1H), 6.90 (m, 3H), 7.08 (d, J ) 7.1 Hz,
1H), 7.28 (t, J ) 7.4 Hz, 1H); 13C NMR (CDCl3) δ 17.6, 21.0,
52.9, 56.1, 69.0, 70.5, 114.0, 115.0, 117.8, 119.5, 130.1, 133.1,
137.6, 159.2, 169.8, 171.1; MS m/ z 335, 276. Anal. Calcd for
C17H21NO6: C, 60.89; H, 6.31. Found: C, 60.78; H, 6.34.
(3R,6S)-2,5-Dim eth oxy-6-isop r op yl-3-(4-flu or o-3-n itr o-
p h en yl)-3,6-d ih yd r o-1,4-p yr a zin e (22). Cuprous cyanide
(89.6 mg, 1.0 mmol) was placed in a 25 mL, two-necked round
bottomed flask, evacuated with a vacuum pump and purged
with argon. The procedure was repeated three times and dry
THF (3 mL) was injected. In another 25 mL two-necked flask
was introduced the (2S)-(+)-2,5-dihydro-3,6-dimethoxy-2-iso-
propylpyrazine (21, 358 mL, 2.0 mmol) and dry THF (2 mL).
The solution was cooled to -78 °C and n-butyllithium (1.6 M,
2 mmol) was added dropwise. After being stirred for 10 min,
it was transferred via cannula to the flask containing the
cuprous cyanide slurry, precooled to 0 °C. The reaction
mixture was further stirred for 5 min after addition, the
resulting tan colored solution was then cooled again to -78
°C and a solution of 4-fluoro-3-nitrobenzyl bromide (20, 234
mg, 1.0 mmol) in THF (3 mL) was introduced dropwise via
syringe. The reaction was stirred at this temperature for 10
min and quenched by addition of 10 mL of aqueous NH4Cl/
NH4OH (9/1). The aqueous layer was extracted with EtOAc.
The combined organic phases were washed with water, dried
(Na2SO4), and evaporated in vacuo. Purification by flash
chromatography (SiO2, heptane/ether ) 10/3) afforded com-
pound 22 as a colorless oil (305 mg, 90%): [R]D -28° (c 0.1,
CHCl3); IR (CHCl3) 2980, 1700, 1535, 1350 cm-1; 1H NMR (200
MHz, CDCl3) δ 0.63 (d, J ) 6.8 Hz, 3H), 0.93 (d, J ) 6.9 Hz,
3H), 2.16 (m, 1H), 3.16 (d, J ) 3.9 Hz, 1H), 3.18 (d, J ) 3.9
Hz, 1H), 3.53 (dd, J ) 3.4, 3.6 Hz, 1H), 3.70 (s, 3H), 3.73 (s,
3H), 4.30 (ddd, J ) 3.4, 3.9, 4.8 Hz, 1H), 7.16 (dd, J ) 8.6,
D-[3-(Allyloxy)p h en yl]glycin e Meth yl Ester 15. A solu-
.
tion of compound 14 (1.3 g, 5.26 mmol) and SnCl2 2H2O (2.37
g, 10.52 mmol) in methanol (50 mL) was stirred for 14 h at
room temperature. The volatile was evaporated in vacuo, and
the residue was partitioned between Et2O and H2O. The
aqueous phase was extracted with Et2O to remove the neutral
species. The aqueous solution was then neutralized with
phosphate buffer (pH 7) and extracted with CH2Cl2. The
combined CH2Cl2 phases were washed with brine, dried (Na2-
SO4), and evaporated in vacuo to afford pure compound 15
(1.08 g, 93%): [R]D -98° (c 0.8, CHCl3); IR (CHCl3) 3400, 1739,
1
1689, 1583, 1497 cm-1; H NMR (300 MHz, CDCl3) δ 3.70 (s,
3H), 4.52 (td, J ) 1.5, 5.3 Hz, 2H), 4.60 (s, 1H), 5.28 (qd, J )
1.5, 10.5 Hz, 1H), 5.42 (qd, J ) 5.3, 17.2 Hz, 1H), 6.03 (tdd, J
) 5.3, 10.5, 17.2 Hz, 1H), 6.82 (td, J ) 1.7, 7.5 Hz, 1H), 6.96
(m, 2H), 7.23 (t, J ) 7.5 Hz, 1H); 13C NMR (CDCl3) δ 52.4,
58.7, 68.9, 113.4, 114.3, 117.6, 119.3, 129.0, 129.8, 133.2, 141.9,
159.0, 174.3; MS m/ z 221, 162; HRMS m/ z 221.1052 (C12H15
-
NO3 requires 221.1051).
D -[2-[(t er t -Bu t yld im e t h ylsilyl)oxy]-1-[3-(a llyloxy)-
p h en yl]eth yl]a m in e (16). A solution of compound 19 (190
.
mg, 0.86 mmol) and SnCl2 2H2O (582 mg, 2.58 mmol) in
methanol (15 mL) was stirred for 20 h at room temperature.
The volatile was evaporated in vacuo, and the residue was
partitioned between Et2O and H2O. The aqueous phase was
extracted with Et2O to remove the neutral species. The
aqueous solution was then basified with aqueous NaHCO3 and
extracted with CH2Cl2. The combined CH2Cl2 phases were
washed with brine, dried (Na2SO4), and evaporated in vacuo
to afford pure compound 3-hydroxyphenylglycine methyl ester
as a colorless oil (124 mg, 74%) which was used without further
purification: [R]D -14.4° (c 0.5, CHCl3); IR (CHCl3) 3300-3500,
2950, 1610, 1490 cm-1; 1H NMR (200 MHz, CDCl3) δ 2.10 (brs,
3H), 3.55 (dd, J ) 8.2, 10.7 Hz, 1H), 3.75 (dd, J ) 4.2, 10.7
Hz, 1H), 4.01 (dd, J ) 4.2, 8.2 Hz, 1H), 4.55 (td, J ) 1.3, 5.2
Hz, 2H), 5.30 (qd, J ) 1.3, 10.4 Hz, 1H), 5.42 (qd, J ) 1.3,
17.3 Hz, 1H), 6.08 (tdd, J ) 5.2, 10.4 and 17.3 Hz, 1H), 6.78-
6.88 (m, 3H), 7.26 (t, J ) 8.0 Hz, 1H); 13C NMR (CDCl3) δ 57.5,
68.2, 69.0, 113.4, 113.7, 117.1, 119.1, 129.8, 133.5, 144.8, 159.2;
MS m/ z 162 (M+ - 31). To a solution of [3-(allyloxy)phenyl]-
glycine methyl ester (220 mg, 1.14 mmol) in dry CH2Cl2 were
added Et3N (639 µL, 4.56 mmol), DMAP (139.3 mg, 1.14 mmol),
and TBDMSCl (515.5 mg, 3.42 mmol) at room temperature.
The reaction mixture was stirred for 5 h at room temperature
and diluted with aqueous NH4Cl. The aqueous phase was
extracted with CH2Cl2. The combined organic phases were
10.7 Hz, 1H), 7.36 (m, 1H), 7.90 (dd, J ) 2.2, 7.3 Hz, 1H); 13
C
NMR (CDCl3) δ 16.6, 19.0, 31.8, 38.7, 52.4, 52.5, 55.9, 60.8,
117.7 (d, J ) 21 Hz), 127.5, 134.9, 136.9, 154.4 (d, J ) 262
Hz), 161.8, 164.5; MS m/ z 338 (M + 1), 336 (M - 1), 295, 184.
Anal. Calcd for C16H20FN3O4: C, 56.97; H, 5.98. Found: C,
57.26; H, 6.06.
D-(4-F lu or o-3-n itr op h en yl)glycin e Meth yl Ester (23).
A solution of 22 (337 mg, 1 mmol) in acetonitrile (5 mL) and
TFA (3 mmol, 0.1 N in water) was stirred at room temperature
for 3 h. The volatile was evaporated and the residue was
basified to pH ) 8 with aqueous NaHCO3. The aqueous
solution was extracted with EtOAc. The combined organic
phase was washed with brine, dried (Na2SO4), and evaporated
in vacuo. Purification by flash chromatography (SiO2, Et2O/

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9319
MeOH ) 10/1) afforded compound 23 as a colorless oil (227.5
mg, 94%): [R]D -14° (c 0.1, CHCl3); IR (CHCl3) 1735, 1537,
1356 cm-1; 1H NMR (200 MHz, CDCl3) δ 1.60 (br s, 2H), 2.90
(dd, J ) 13.8, 7.8 Hz, 1H), 3.13 (dd, J ) 13.8, 5.1 Hz, 1H),
3.70 (m, 1H), 3.73 (s, 3H), 7.23 (dd, J ) 10.6, 8.5 Hz, 1H), 7.50
(m, 1H), 7.93 (dd, J ) 7.1, 2.2 Hz, 1H); 13C NMR (CDCl3) δ
39.7, 52.3, 55.4, 118.5 (d, J ) 21 Hz), 126.0, 134.0, 136.0, 154.5
(d, J ) 262 Hz), 174; MS m/ z (CI) 243 (M+ + 1). Anal. Calcd
for C10H11FN2O4: C, 49.59; H, 4.58. Found: C, 49.36; H, 4.64.
Com p ou n d 25. To a solution of amino ester 23 (300 mg,
1.24 mmol) in CH2Cl2 (10 mL) was added EDC (260 mg, 1.36
mmol) and N-Boc-N-methyl-D-leucine (340 mg, 1.40 mmol).
After being stirred at room temperature for 5 h, the reaction
mixture was diluted with H2O and the aqueous phase was
extracted with CH2Cl2. The combined organic phase was
washed with brine, dried (Na2SO4), and evaporated in vacuo.
The crude product was purified by flash chromatography (SiO2,
CH2Cl2/MeOH ) 100/1) to afford dipeptide 25 (550 mg, 95%):
mp 66-68 °C; [R]D +50° (c 0.15, CHCl3); IR (CHCl3) 2950, 1743,
and LiBH4 (28 mg, 1.32 mmol). Stirring was continued at
room temperature for 1 h. The reaction was quenched by
addition of 2 N HCl and then ajusted to pH ) 7. The aqueous
solution was extracted with EtOAc. The combined organic
phase was washed with brine, dried (Na2SO4), and evaporated
in vacuo. The crude product was passed through a short pad
of Sephadex LH 20 (CH2Cl2, then EtOAc). The so-obtained
amino alcohol was dissolved in dry DMF, dipeptide 26 (100
mg, 0.22 mmol), DPPA (56 µL, 0.26 mmol), and Et3N (34 µl,
0.24 mmol) were added successively. After being stirred for 3
h at room temperature under argon, the reaction mixture was
diluted with water. The aqueous solution was extracted with
EtOAc. The combined organic phase was washed with water,
dried (Na2SO4), and evaporated in vacuo. Purification by
preparative TLC (EtOAc/ether ) 1/2) afforded tetrapeptide 30
in 55% yield (94 mg); mp 85-90°; [R]D +12.0° (c 0.2, CHCl3);
IR (CHCl3) 3200-3400, 1700, 1680, 1550 cm-1; 1H NMR (300
MHz, CDCl3) δ -0.05 (s, 3H, SiMe), -0.03 (s, 3H, SiMe), 0.87
(s, 9H, SiBut), 0.89 (d, J ) 5.7 Hz, 3H, CHMe2), 0.92 (d, J )
6.5 Hz, 3H, CHMe2), 1.21 (d, J ) 6.9 Hz, 3H, CHMe), 1.43 (m,
1H, CH2CHMe2), 1.47 (s, 9H, But), 1.46-1.48 (m, 1H,
CH2CHMe2), 2.70 (s, 3H, NMe), 2.92 (dd, J ) 7.0, 13.9 Hz,
1H, H15), 3.05 (dd, J ) 6.3, 13.9 Hz, 1H, H15′), 3.80 (dd, J )
5.4, 10.2 Hz, 1H, CH2OTBDMS), 3.88 (dd, J ) 4.5, 10.2 Hz,
1H, CH2OTBDMS), 4.50 (m, 1H, H11), 4.63 (dd, J ) 5.6, 9.6
Hz, 1H, CHCH2CHMe2), 4.76 (m, 1H, H14), 4.86 (m, 1H, H8),
6.77 (dd, J ) 2.3, 8.0 Hz, 1H, H4), 6.80 (d, J ) 8.0 Hz, 1H,
H6), 6.86 (s, 1H, H21), 7.09 (dd, J ) 8.5, 10.5 Hz, 2H, H19
and NH), 7.18 (t, J ) 8.0 Hz, 2H, H5 and H20), 7.69 (dd, J )
2.0, 6.9 Hz, 1H, H17), 7.83 (brs, 1H, NH), 7.93 (brs, 1H, NH);
13C NMR (CDCl3) δ -5.5, -5.4, 18.3, 18.6, 21.7, 23.9, 24.9, 25.9,
28.4, 29.4, 36.7, 38.0, 49.4, 53.9, 55.4, 57.0, 66.0, 81.1, 114.7,
118.3 (d, J ) 21 Hz), 126.7, 128.8, 129.8, 132.2, 136.7, 141.2,
151.6, 154.0 (d, J ) 262 Hz), 157.0, 168.3, 171.6, 175.8; FABMS
(Thio/NaCl) m/ z 798 (M + Na+), 776 (M + H+). Anal. Calcd
for C38H58FN5O9Si: C, 58.82; H, 7.53. Found: C, 59.01; H,
7.81.
1
1680, 1550, 1350 cm-1; H NMR (200 MHz, CDCl3) δ 0.89 (d,
J ) 6.4 Hz, 3H), 0.93 (d, J ) 6.6 Hz, 3H), 1.43 (s, 9H), 1.63
(m, 3H), 2.66 (s, 3H), 3.06 (dd, J ) 6.0, 14.0 Hz, 1H), 3.26 (dd,
J ) 5.5, 14.0 Hz, 1H), 3.76 (s, 3H), 4.60 (t, J ) 7.6 Hz, 1H),
4.83 (m, 1H), 6.76 (br s, 1H), 7.20 (t, J ) 8.5 Hz, 1H), 7.37 (m,
1H), 7.80 (dd, J ) 2.0, 7.2 Hz, 1H); 13C NMR (CDCl3) δ 21.8,
23.1, 24.7, 28.2, 31.4, 36.3, 37.0, 52.9, 56.5, 57.0, 81.0, 118.6
(d, J ) 21 Hz), 126.5, 133.5, 136.4, 137.5, 154.6 (d, J ) 262
Hz), 171.0, 171.5; MS m/ z (CI) 470 (M+ + 1), 414, 370. Anal.
Calcd for C22H32FN3O7: C, 56.28; H, 6.87. Found: C, 56.65;
H, 6.67.
Com p ou n d 26. A solution of 25 (469 mg, 1 mmol) in
methanol (6 mL) and water (2 mL) was stirred for 5 h in the
presence of K2CO3 (207 mg, 1.5 mmol). The volatile was
removed and the residue was acidified. The aqueous solution
was extracted with EtOAc, and the combined organic phases
were washed with brine, dried (Na2SO4), and evaporated to
give 26 as a yellowish solid in quantitative yield: mp 140-
145 °C; [R]D +28° (c 0.1, MeOH); IR (CHCl3) 3400-3500, 1730,
Com p ou n d 31. To a solution of compound 30 (77 mg, 0.1
mmol) in DMF (10 mL) was added dry CsF (304 mg, 2.0 mmol).
The mixture was stirred at room temperature under argon for
15 h and then diluted with water. The aqueous solution was
extracted with EtOAc. The combined organic phases were
washed with water, dried (Na2SO4), and evaporated in vacuo.
Purification by preparative TLC (ether/EtOAc ) 2/1) furnished
the macrocycle 31 (40 mg, 63%); mp 120-121; [R]D -71° (c
1
1680, 1630, 1540, 1400, 1340 cm-1; H NMR (300 MHz, CD3-
COCD3) δ 0.87 (d, J ) 6.6 Hz, 3H), 0.89 (d, J ) 6.6 Hz, 3H),
1.43 (s, 9H), 1.4-1.6 (m, 3H), 2.60 (s, 3H), 3.15 (dd, J ) 6.2,
13.8 Hz, 1H), 3.38 (dd, J ) 5.0, 14.0 Hz, 1H), 4.63 (m, 1H),
4.80 (m, 1H), 7.25 (m, 1H), 7.37 (dd, J ) 8.6, 11.2 Hz, 1H),
7.70 (m, 1H), 7.79 (dd, J ) 1.8, 8.2 Hz, 1H); 13C NMR (CDCl3)
δ 21.9, 23.6, 25.5, 28.6, 31.4, 36.9, 37.8, 54.2, 57.1, 80.4, 119.0
(d, J ) 20.8 Hz), 127.6 (d, J ) 3.8 Hz), 136.5 (d, J ) 3.8 Hz),
138.0 (d, J ) 9.4 Hz), 150.7, 154.8 (d, J ) 258.4 Hz), 171.8,
173.4; MS m/ z (CI) 456 (M+ + 1), 400, 356.
0.1, CHCl3); IR (CHCl3) 3300-3400, 1720, 1600, 1530 cm-1
;
1H NMR (400 MHz, CDCl3, 264K) δ 0.94 (d, J ) 6.4 Hz, 3H,
CHMe2), 0.97 (d, J ) 6.6 Hz, 3H, CHMe2), 1.35 (d, J ) 7.1 Hz,
3H, CHMe), 1.49 (s, 9H, But), 1.48-1.52 (m, 1H, CHMe2), 1.73
(t, J ) 7.4 Hz, 2H, CH2CHMe2), 2.75 (dd, J ) 5.4, 13.1 Hz,
1H, H15), 2.91 (s, 3H, NMe), 3.65 (dd, J ) 5.1, 13.1 Hz, 1H,
H15′), 3.80 (m, 1H, CH2OH), 3.88 (m, 1H, CH2OH), 4.51 (m,
1H, H11), 4.66 (t, J ) 7.4 Hz, 1H, CHCH2CHMe2), 5.01 (m,
2H, H8 and H14), 5.81 (s, 1H, H21), 6.72 (br s, 1H, NH), 6.79
(br d, J ) 6.9 Hz, 1H, NH), 6.91 (d, J ) 7.8 Hz, 1H, H6), 7.01
(d, J ) 8.6 Hz, 1H, H19), 7.19 (dd, J ) 2.0, 7.8 Hz, 1H, H4),
7.35 (t, J ) 7.8 Hz, 1H, H5), 7.39 (br s, 1H, NH9), 7.54 (dd, J
) 1.8, 8.6 Hz, 1H, H20), 7.83 (br s, 1H, H17); 13C NMR (CDCl3)
δ 21.3, 21.7, 23.6, 24.3, 28.2, 36.5, 37.9, 39.3, 49.6, 53.6, 55.4,
56.8, 65.2, 81.4, 112.8, 116.8, 120.9, 125.3, 126.3, 130.4, 134.5,
137.2, 139.6, 143.1, 148.7, 157.1, 159.9, 168.8, 171.6, 172.3;
FABMS (Thio/NaCl) m/ z 664 (M + Na+).
Com p ou n d 28. A solution of 16 (75 mg, 0.25 mmol),
N-alloc-L-alanine 27 (43 mg, 0.25 mmol) and EDC (53 mg, 0.27
mmol) in CH2Cl2 (4 mL) was stirred at room temperature
under argon for 2 h. The reaction mixture was then diluted
with water and extracted with CH2Cl2. The combined organic
phases were washed with brine, dried (Na2SO4), and evapo-
rated in vacuo. The crude product was purified by flash
chromatography (SiO2, CH2Cl2) to afford compound 28 (101
mg, 88%) as a colorless oil: [R]D -19.5° (c 0.35, CHCl3); IR
(CHCl3) 3430, 1720, 1680, 1500 cm-1 1H NMR (300 MHz,
;
CDCl3) δ -0.1 (s, 3H, SiMe), -0.05 (s, 3H, SiMe), 0.85 (s, 9H,
SiBut), 1.40 (d, J ) 6 Hz, 3H, CHMe), 3.75 (dd, J ) 4.4, 10.3
Hz, 1H, CH2OTBDMS), 3.90 (dd, J ) 4.3, 10.3 Hz, 1H, CH2-
OTBDMS), 4.29 (m, 1H, CHMe), 4.52 (td, J ) 1.5, 5.2 Hz, 2H,
OCH2CHCH2), 4.58 (br d, J ) 5.5 Hz, 2H, OCH2CHCH2), 4.95
(dt, J ) 4.3, 7.5 Hz, 1H, ArCH), 5.21 (qd, J ) 1.3, 10.5 Hz,
1H, OCH2CHCH2), 5.27 (qd, J ) 1.5, 10.5 Hz, 1H, OCH2-
CHCH2), 5.35 (qd, J ) 1.3, 17.3 Hz, 1H, OCH2CHCH2), 5.40
(qd, J ) 1.5, 17.2 Hz, 1H, OCH2CHCH2), 5.9 (m, 1H,
OCH2CHCH2), 6.05 (tdd, J ) 5.2, 10.5 and 17.2 Hz, 1H,
OCH2CHCH2), 6.72 (d, J ) 7.3 Hz, 1H, NH), 6.78-6.88 (m,
3H - aromatic + NH), 7.2 (t, J ) 8.4 Hz, 1H, H - aromatic);
13C NMR (CDCl3) δ -6.0, 18.3, 19.0, 25.9, 50.7, 54.7, 66.0, 66.2,
66.9, 113.8, 117.6, 118.0, 119.3, 123.4, 132.7, 133.4, 141.6,
155.0, 158.8, 171.7; MS m/ z 462, 447, 405. Anal. Calcd for
C24H38N2O5Si: C, 62.31; H, 8.28. Found: C, 62.34; H, 8.51.
Com p ou n d 30. To the solution of 28 (101 mg, 0.22 mmol)
in dry THF (3 mL) were added Pd(PPh3)4 (11 mg, 0.01 mmol)
Com p ou n d 46a . Cyclization of 45a under conditions
described for 30 gave compound 46a in 70-75% yield: mp
150-153 °C; [R]D -90° (c 0.4, CHCl3); IR (CHCl3) 3618, 3435,
1
1718, 1680, 1668, 1537, 1480, 1360 cm-1; H RMN (acetone-
d6) δ 1.33 (d, J ) 7.0 Hz, 3H, CH3Ala), 1.47 (s, 9H, But), 3.06
(m, 1H, H15), 3.50 (dd, J ) 4.6, 13.1 Hz, 1H, H15′), 3.77 (m,
2H H22), 4.16 (br d, 1H, NHBoc), 4.45 (m, 1H, H11), 4.50 (m,
1H, H14), 4.70 (m, 1H, H8), 6.16 (br s, 1H, H21), 6.40 (br d,
1H, NH12), 6.95 (d, J ) 8.1Hz, 1H, H6), 7.02 (d, J ) 8.1Hz,
1H, H4), 7.07 (d, J ) 8.3Hz, 1H, H19), 7.27 (t, J ) 8.1Hz, 1H,
H5), 7.45 (m, 2H, H20 + NH9), 8.05 (br s, 1H, H17); 13C RMN
(CDCl3) δ 18.7, 28.3, 37.7, 49.7, 55.9, 56.0, 64.9, 81.0, 113.1,
116.9, 121.0, 125.6, 126.4, 130.2, 134.4, 136.9, 140.1, 143.0,

9320 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
148.9, 155.3, 159.9, 169.4, 172.5; MS (CI) m/ z 515 (M + 1)
497, 459, 415.
was hydrogenated at 1 atm for 2 h. The reaction mixture was
filtered through
a short pad of Celite, the filtrate was
evaporated in vacuo and purified by flash chromatography to
afford 35 (4.3 g, 92%): mp 45 °C; [R]D +165.8° (c 0.5, CHCl3);
IR (CHCl3) 3450, 3010, 1793, 1706, 1600, 1387 cm-1; 1H NMR
(200 MHz, CDCl3) δ 1.31 (d, J ) 6.0 Hz, 6H), 1.43 (s, 9H),
2.84 (dd, J ) 10.2, 13.4 Hz, 1H), 3.39 (dd, J ) 2.6, 13.4 Hz,
1H), 4.08 (dd, J ) 7.3, 9.1 Hz, 1H), 4.13 (dd, J ) 2.6, 9.1 Hz,
1H), 4.54 (septet, J ) 6.0 Hz, 1H), 4.57 (m, 1H), 5.49 (d,
J ) 7.9 Hz, 1H), 6.57 (d, J ) 7.9 Hz, 1H), 6.8-7.5 (m, 9H);
13C NMR (CDCl3) δ 21.8, 28.1, 37.4, 55.5, 56.4, 66.0, 69.6,
79.9, 115.5, 116.0, 119.8, 123.4, 127.1, 128.8, 129.3, 129.7,
135.0, 137.0, 148.9, 152.1, 154.7, 158.0, 171.3. Anal. Calcd
for C26H32N2O6: C, 66.65; H, 6.88; N, 5.98. Found: C, 66.37;
H, 6.70; N, 5.71.
Com p ou n d 32. Following the procedure detailed for 12,
hydrolysis of 35 afforded compound 32 in 92% yield: [R]D
+109.5° (c 0.4, CHCl3); IR (CHCl3) 3446, 3313, 2939, 1727,
4660, 1616, 1607, 1485, 1350 cm-1; 1H NMR (200 MHz, CDCl3,
2 rotamers) δ 1.21 (s, OBut), 1.31 (d, J ) 6.0 Hz, 6H, OCHMe2),
1.41 (s, OBut), 4.52 (septet, J ) 6.0 Hz, 1H, OCHMe2), 5.06
(d, J ) 4.3 Hz, ArCH), 5.27 (d, J ) 6.8 Hz, ArCH), 5.50 (br s,
1H, NH), 6.8-7.2 (m, 4H, aromatics), 7.67 (brs, OH); 13C NMR
(CDCl3, 62.5 MHz) δ 22.2 (22.3), 28.2 (28.5), 57.8 (59.1), 70.1,
80.6 (81.8), 114.7 (114.9), 115.9, 119.4 (119.7), 129.6 (130.1),
138.2 (139.9), 155.3 (157.1), 158.2 (158.4), 173.7 (175.3); MS
(EI) m/ z 309, 292, 264. Anal. Calcd for C16H23NO5: C, 62.12;
H, 7.49; N, 4.53. Found: C, 61.91; H, 7.52; N, 4.65.
Com p ou n d 46b. Cyclization of 45b under conditions
described for 30 gave compound 46b in 75% yield: [R]D -115°
(c ) 0.1, CHCl3); IR (CHCl3) 3618, 3420, 1710, 1680, 1660,
1
1537, 1490, 1480 cm-1; H NMR (300 MHz, CDCl3) δ 1.43 (d,
J ) 6.8 Hz, 3H, MeAla), 1.49 (s, 9H, But), 2.70 (dd, J ) 9.8,
13.3 Hz, 1H, H15), 3.31 (s, 3H, OMe), 3.53 (dd, J ) 4.8, 13.3
Hz, 1H, H15′), 3.71 (m, 1H, H22), 3.78 (m, H22′), 4.20 (m, 1H,
H11), 4.41 (m, 1H, H14), 4.98 (m, 1H, H8), 5.54 (d, J ) 7.6
Hz, 1H, NHBoc), 5.91 (br s, 1H, H21), 5.98 (br d, 1H, NH12),
6.41 (br d, 1H, NH9), 6.92 (dd, J ) 1.8, 7.9 Hz, 1H, H6), 7.13
(d, J ) 8.4 Hz, 1H, H19), 7.17 (dd, J ) 2.0, 7.9 Hz, 1H, H4),
7.34 (t, J ) 7.9 Hz, 1H, H5), 7.60 (dd, J ) 2.0, 8.4 Hz, 1H,
H20), 7.67 (brs, 1H, H17); 13C NMR (CDCl3) δ 21.3, 28.3, 39.2,
49.1, 50.1, 52.8, 53.0, 59.2, 81.7, 113.7, 117.2, 120.7, 126.0,
126.9, 129.7, 130.2, 135.4-142.7 (4 C), 155.2, 156.8, 171.5;
FABMS (Thio/NaCl) m/ z 551 (M + Na+), 529 (M + H+);
selected NOES H17-H15, NHBoc; H20-H14, H15′, H19; H6-
H8, H22; NH9-H21, H8, MeAla; NH12-H14, NHBoc; H21-H8;
NHBoc-H17, H12, H14, H15; H8-H6, NH9, H21, H22; H14-
H20, H12, H15, H15′, NHBoc, H11-NH12, NH9; MeAla-NH9.
Com p ou n d 3. To a solution of 31 (38.5 mg, 0.06 mmol) in
acetonitrile (6 mL) was added concentrated HCl (0.6 mL)
dropwise. After being stirred for 1 h at room temperature,
the solution was carefully basified (pH ) 8) by addition of
aqueous NaHCO3, the pure product 3′ (26 mg, 82%) was
obtained by simple extraction with AcOEt; mp 138-140 °C;
[R]D -70° (c 0.1, CHCl3); IR (CHCl3) 3700, 3420, 3340, 1700-
Com p ou n d 36. To a solution of amino acid 32 (450 mg,
1.45 mml) in CH2Cl2 (10 mL) was added a solution of amino
alcohol 16 (406 mg, 1.32 mmol) in CH2Cl2 (3 mL), HOBt (230
mg, 1.7 mmol) and EDC (300 mg, 1.6 mmol) at 0 °C. After
being stirred for 30 min at 0 °C, the reaction mixture was
diluted with aqueous NH4Cl (15 mL) and was extracted with
CH2Cl2. The combined organic extracts were washed with
brine, dried (Na2SO4), and evaporated. Flash chromatography
(SiO2, EtOAc/heptane ) 1/6) afforded dipeptide 36 (728 mg,
92%): mp ) 85 °C; [R]D +49.5° (c 0.2, CHCl3); IR (CHCl3) 3418,
1670, 1590, 1530, 1250 cm-1 1H NMR (400 MHz, 300K, 20
;
mg/0.4 mL CDCl3) δ 0.96 (d, J ) 6.4 Hz, 3H, CH3Leu), 0.99
(d, J ) 6.4 Hz, 3H, H28, C3Leu), 1.24 (s, NHLeu), 1.35 (d, J )
6.9 Hz, 3H, CH3 Ala), 1.41-1.76 (m, 3H, CH2 Leu and CHLeu),
2.40 (s, 3H, N-CH3), 2.75 (dd, J ) 7.0, 13.3 Hz, 1H, H15), 3.07
(dd, J ) 4.8, 9.0 Hz, 1H, H25), 3.55 (dd, J ) 4.4, 13.3 Hz, 1H,
H15′), 3.89 (m, 2H, CH2OH), 4.32 (m, 1H, H11), 4.80 (m, 2H,
H8 + H14), 5.62, 5.78 (br s, OH), 5.97 (s, 1H, H21), 6.48 (d, J
) 6.2 Hz, 1H, NH12), 6.91 (d, J ) 7.7 Hz, 1H, H6), 7.00 (d, J
) 6.9 Hz, 1H, NH23), 7.02 (d, J ) 8.6 Hz, 1H, H19), 7.17 (dd,
J ) 2.4, 8.1 Hz, 1H, H4), 7.37 (t, J ) 7.9 Hz, 1H, H5), 7.56 (d,
J ) 1.8, 8.6 Hz, 1H, H20), 7.75 (s, J ) 1.8 Hz, 1H, H17), 8.11
(br s, 1H, NH9); FABMS (Thio/NaCl) m/ z 564 (M + Na+), 542
(M +H+).
2987, 2956, 2937, 1718, 1680, 1606, 1490 cm-1 1H NMR
;
(CDCl3, 250 MHz) δ -0.20 (s, 3H), -0.09 (s, 3H), 0.80 (s, 9H),
1.27 (d, J ) 5.2 Hz, 3H), 1.29 (d, J ) 5.2 Hz, 3H), 1.39 (s, 9H),
3.69 (dd, J ) 3.6 Hz, 10.2 Hz, 1H), 3.88 (dd, J ) 4.0 Hz, 10.2
Hz, 1H), 4.33 (br d, J ) 5.2 Hz, 1H), 4.49 (septet, J ) 5.2 Hz,
1H), 4.91 (td, J ) 3.8, 7.6 Hz, 1H), 5.12 (br s, 1H), 5.25 (qd, J
) 1.3, 10.5 Hz, 1H), 5.37 (qd, J ) 1.3, 17.3 Hz, 1H), 5.84 (br s,
1H), 6.00 (tdd, J ) 5.2, 10.5, 17.3 Hz, 1H), 6.44-6.52 (m, 3H),
6.71 (dd, J ) 2.5, 8.1 Hz, 1H), 6.81-6.85 (m, 2H), 6.91 (d, J )
7.8 Hz, 1H), 7.07 (t, J ) 7.8 Hz, 1H), 7.26 (t, J ) 8.1 Hz, 1H);
13C NMR (CDCl3) δ -5.7, -5.6, 18.2, 22.1, 25.9, 28.4, 54.7,
58.9, 66.3, 68.7, 69.9, 80.0, 112.6, 114.0, 114.2, 116.0, 117.5,
119.0, 119.4, 129.2, 130.3, 133.4, 141.5, 158.7, 169.2; MS
Compound 3 was obtained by heating the acetone solution
of 3′ for 30 min: mp 120-125 °C; [R]D -160° (c 0.15, EtOH);
1
IR (CHCl3) 3450, 3320, 1700, 1660, 1530 cm-1; H NMR (400
MHz, Me2CO-d6) δ 0.84 (d, J ) 6.6 Hz, 3H, MeLeu), 0.88 (d, J
) 6.6 Hz, 3H, MeLeu), 1.22 (d, J ) 7.2 Hz, 3H, MeAla), 1.28
(m, 1H, NHLeu), 1.58 (m, 2H, CH2Leu), 1.74 (m, 1H, CH Me2-
Leu), 2.42 (s, 3H, NMe), 3.24 (dd, J ) 2.5, 7.5 Hz, 1H,
N-CHCOleu), 3.34 (dd, J ) 14.0, 5.0Hz, 1H, H15), 3.50 (m,
2H, CH2-O), 3.70 (dd, J ) 14.0, 5.0Hz, 1H, H15′), 3.80 (t, J )
6.5 Hz, 1H, OH), 4.53 (m, 2H, H11 + H14), 4.90 (m, 1H, H8),
6.36 (s, 1H, H21), 6.92 (d, J ) 7.5 Hz, 1H, H6), 7.00 (d, J )
8.5 Hz, 1H, H19), 7.09 (dd, J ) 8 Hz, 3Hz, 1H, H4), 7.17 (d, J
) 9 Hz, 1H, NH12), 7.26 (t, J )7.5 Hz, 1H, H5), 7.68 (d, J )
9 Hz, 1H, NH9), 7.79 (dd, J )7.5 Hz, 1H, H20), 7.91 (d, J ) 2
m/ z 598 (M
: C, 66.19; H, 8.42; N, 4.68. Found: C, 66.49; H, 8.51;
+), 541, 525, 497, 482. Anal. Calcd for C33H50N2-
SiO6
N, 4.52.
Com p ou n d 37. To a solution of dipeptide 36 (99 mg, 0.165
mmol) in THF (1 mL) was added NaBH4 (38 mg, 1 mmol) and
Pd(PPh3)4 (9.6 mg, 8.27 µmol) at 0 °C. After being stirred for
1 h at room temperature, the reaction mixture was diluted
with aqueous NH4Cl (10 mL), and the aqueous solution was
extracted with EtOAc. The combined organic extracts were
washed with brine, dried (Na2SO4), and evaporated. Flash
chromatography (SiO2, EtOAc/heptane ) 1/6 then 1/3) afforded
compound 37 (78.3 mg, 85%): [R]D +60.6° (c 0.3, CHCl3); IR
(CHCl3) 3600, 3425, 2975, 2963, 2931, 1712, 1686, 1606, 1480
1
Hz, 1H, H17); H NMR (400 MHz, CDCl3) δ 0.86 (d, J ) 6.8
Hz, 3H, MeLeu), 0.88 (d, J ) 6.8 Hz, 3H, MeLeu), 1.31 (d, J )
7.2 Hz, 3H, MeAla), 1.37 (m, 1H, CH2Leu), 1.66 (m, 1H, CH2-
Leu), 1.72 (m, 1H CHMe2Leu), 2.40 (s, 3H, NMe), 3.12 (dd, J
) 5.2, 14.0 Hz, 1H, H15), 3.22 (dd, J ) 2.6, 6.9 Hz, 1H,
COCHNLeu), 3.46 (dd, J ) 8.3, 11.3 Hz, 1H, OCH2), 3.61 (dd,
J ) 4.6, 11.3 Hz, 1H, OCH2), 3.76 (dd, J ) 4.6, 14.0 Hz, 1H,
H15′), 4.17 (m, 1H, H14), 4.65 (m, 1H, H11), 5.01 (dt, J ) 4.6,
8.5 Hz, 1H, H8), 6.39 (s, 1H, H21), 6.68 (d, J ) 9.1 Hz, 1H,
NH12), 6.86 (d, J ) 7.6 Hz, 1H, H6), 6.98 (d, J ) 8.4 Hz, 1H,
H19), 7.19 (dd, J ) 2.5, 7.6 Hz, 1H, H4), 7.22 (br d, 1H, NH9),
7.25 (t, J ) 7.6 Hz, 1H, H5), 7.72 (dd, J ) 2.2, 8.4 Hz, 1H,
H20), 7.74 (d, J ) 2.2 Hz, 1H, H17); 13C NMR (CDCl3) δ 18.7,
22.6, 23.7, 26.2, 33.1, 36.9, 38.7, 49.7, 57.3, 58.3, 62.4, 67.2,
115.7, 116.6, 122.5, 126.2, 128.3, 129.9, 136.8, 139.0, 143.2,
150.8, 162.5, 167.5, 172.7; FABMS (Thio/NaCl) m/ z 564 (M +
Na+), 542 (M + H+).
1
cm-1; H NMR (CDCl3, 250 MHz) δ -0.27 (s, 3H), -0.10 (s,
3H), 0.75 (s, 9H), 1.27 (d, J ) 6.0 Hz, 3H), 1.32 (d, J ) 6.0 Hz,
3H), 1.43 (s, 9H), 3.67 (dd, J ) 3.5 Hz, 10.1 Hz, 1H), 3.85 (dd,
J ) 3.8, 10.1 Hz, 1H), 4.52 (septet, J ) 6.0 Hz, 1H), 4.85 (td,
J ) 3.8, 7.6 Hz, 1H), 5.17 (br s, 1H), 5.90 (br s, 1H), 6.18 (s,
1H), 6.46 (m, 2H), 6.61 (dd, J ) 2.5, 8.0 Hz, 1H), 6.81-6.92
(m, 2H), 6.99 (d, J ) 7.5 Hz, 1H), 7.01 (t, J ) 7.9 Hz, 1H),
7.29 (t, J ) 7.8 Hz, 1H); 13C NMR (CDCl3, 50.03 MHz) δ -5.8,
-5.6, 18.2, 22.1, 25.9, 28.4, 54.7, 58.9, 66.1, 70.6, 80.2, 113.6,
114.4, 115.0, 116.2, 118.2, 120.2, 129.4, 130.3, 130.4, 140.5,
141.3, 156.0, 158.5, 169.5; MS m/ z 558 (M+), 501, 457; HRMS
m/ z 558.3110 (C30H46N2SiO6 requires 558.3125).
Com p ou n d 35. A suspension of 34 (3.94 g, 10 mmol),
Boc2O (3.27 g, 15 mmol) and Pd/C (10%, 400 mg) in EtOAc

Binding Pockets of Vancomycin and Teicoplanin
J . Org. Chem., Vol. 61, No. 26, 1996 9321
Com p ou n d 38. A solution of compound 37 (152 mg, 0.27
mmol), TBDMSOTf (375 µL, 1.63 mmol) and 2,6-lutidine (159
µL, 1.36 mmol) was stirred at room temperature for 20 min.
The reaction was quenched by addition of aqueous NH4Cl and
acidified with 3 N HCl to pH ) 2. The resulting mixture was
stirred for 15 min, neutralized with phosphate buffer (pH )
7), and extracted with CH2Cl2. The combined organic extracts
were washed with brine, dried (Na2SO4), and evaporated.
Flash chromatography (SiO2, EtOAc/heptane ) 1/2 then 1/1)
afforded compound 38 (145 mg, 76%): [R]D +10.8° (c 0.5,
CHCl3); IR (CHCl3) 3418, 3368, 2956, 2931, 2861, 1675, 1600,
3H, OCHMe2), 1.31 (d, J ) 6.0 Hz, 3H, OCHMe2), 1.45 (s, 9H,
OBut), 2.78 (dd, J ) 7.8, 13.8 Hz, 1H, H15), 3.55 (dd, J ) 4.9,
13.8 Hz, 1H, H15′), 3.75 (dd, J ) 3.3, 11.4 Hz, 1H, H22), 3.85
(dd, J ) 4.8, 11.4 Hz, 1H, H22′), 4.49 (septet, J ) 6.0 Hz, 1H,
OCHMe2), 4.52-4.75 (m, 3H, H8, H14, NH12), 5.10 (brs, 1H,
NH), 5.45 (d, J ) 7.8 Hz, 1H, H11), 6.03 (br s, 1H, H21), 6.31
(br s, 1H, NH), 6.54 (d, J ) 8.0 Hz, 1H, H27), 6.71 (br s, 1H,
H25), 6.78 (dd, J ) 2.4, 8.0 Hz, 1H, H29), 6.87 (d, J ) 7.9 Hz,
1H, H4), 7.08 (d, J ) 8.5 Hz, 1H, H19), 7.19 (dd, J ) 2.5, 7.9
Hz, 1H, H6), 7.24 (t, J ) 8.0 Hz, 1H, H28), 7.32 (t, J ) 7.9 Hz,
1H, H5), 7.60 (d, J ) 8.5 Hz, 1H, H20), 7.85 (d, J ) 1.7 Hz,
1
1487 cm-1
;
1H NMR (CDCl3, 200 MHz) δ -0.11 (s, 3H, Me),
1H, H17); H NMR (CD3CN, 400 MHz, 313 K) δ 1.25 (d, J )
-0.05 (s, 3H, Me), 0.19 (s, 6H, 2Me), 0.85 (s, 9H), 0.99 (s, 9H),
1.32 (d, J ) 6.0 Hz, 6H), 3.75, (dd, J ) 3.9 Hz, 10.1 Hz, 1H),
3.84 (dd, J ) 4.3 Hz, 10.1 Hz, 1H), 4.50 (s, 1H), 4.51 (septet,
J ) 6.0 Hz, 1H), 4.94 (td, J ) 4.1, 8.2 Hz, 1H), 6.6-7.3 (m,
8H), 7.68 (d, J ) 8.2 Hz, 1H); 13C NMR (CDCl3) δ -5.6, -5.5,
-4.3, 18.3, 22.2, 25.8, 25.9, 29.0, 54.1, 60.1, 66.2, 69.8, 114.7,
115.3, 118.9, 119.1, 120.1, 122.0, 129.2, 130.0, 142.0, 142.7,
155.7, 158.4, 172.3; MS (EI) m/ z 572 (M+), 557, 515, 457, 427.
Anal. Calcd for C31H52N2Si2O4: C, 64.99; H, 9.15; N, 4.89.
Found: C, 65.19; H, 9.17; N, 4.74.
Com p ou n d 40. A solution of dipeptide 38 (82.5 mg, 0.145
mmol), amino acid 39 (43 mg, 0.131 mmol), EDC (30 mg, 0.15
mmol), and HOBt (26.5 mg, 0.19 mmol) in CH2Cl2 (5 mL) was
stirred at room temperature for 40 min. The reaction mixture
was diluted with phosphate buffer (pH ) 7) and extracted with
CH2Cl2. The combined organic extracts were washed with
brine, dried (Na2SO4), and evaporated. Flash chromatography
(SiO2, EtOAc/heptane ) 1/3) afforded compound 40 (109 mg,
95%): mp 59 °C; [R]D +40.6° (c 0.2, CHCl3); IR (CHCl3) 3425,
2950, 2931, 1718, 1679, 1587, 1481 cm-1; 1H NMR (CDCl3, 250
MHz) δ -0.19 (s, 3H), -0.10 (s, 3H), 0.12 (s, 6H), 0.78 (s, 9H),
0.95 (s, 9H), 1.30 (m, 6H), 1.39 (s, 9H), 2.95 (dd, J ) 6.3, 13.5
Hz, 1H), 3.10 (dd, J ) 6.5, 13.5 Hz, 1H), 3.68 (dd, J ) 3.6,
10.1 Hz, 1H), 3.85 (dd, J ) 4.1, 10.1 Hz, 1H), 4.4-4.6 (m, 2H),
4.85 (m, 1H), 5.14 (d, J ) 8.3 Hz, 1H), 5.38 (d, J ) 6.2 Hz,
1H), 6.3-7.4 (m, 12H), 7.71 (dd, J ) 2.0, 7.0 Hz, 1H); 13C NMR
(CDCl3): δ -5.7, -5.6, -4.4, 18.2, 22.1, 25.8, 25.9, 28.3, 29.8,
37.8, 54.8, 57.4, 66.2, 69.9, 80.5, 115.0, 115.9, 118.3 (d, J )
16.6 Hz), 118.9, 119.2 (d, J ) 9.7 Hz), 126.9, 129.1, 130.5,
133.7, 136.5 (d, J ) 7.7 Hz), 138.9, 141.3, 151.5, (d, J ) 267.0
Hz), 158.7, 168.6, 169.7; FABMS m/ z 883 (M + H+). Anal.
Calcd for C45H67FN4Si2O9: C, 61.20; H, 7.65; N, 6.34. Found:
C, 61.36; H, 7.82; N, 6.39.
6.0 Hz, 6H, OCHMe2), 1.44 (s, 9H, OBut), 2.97 (dd, J ) 3.6,
13.9 Hz, 1H, H15), 3.44 (dd, J ) 5.0, 13.9 Hz, 1H, H15′), 3.72
(m, 2H, H22), 4.43 (m, 1H, H14), 4.57 (m, 2H, H8 and
OCHMe2), 5.30 (d, J ) 8.0 Hz, 1H, H11), 5.80 (br d, 1H, NH23),
6.17 (s, 1H, H21), 6.81 (m, 3H, H25, H27 and H29), 6.98 (m,
2H, H6 and NH9), 7.03 (br d, 1H, NH12), 7.11 (d, J ) 8.5 Hz,
1H, H19), 7.15 (m, 1H), 7.21 (t, J ) 7.6 Hz, 1H, H28), 7.38 (t,
J ) 7.9 Hz, 1H, H5), 7.47 (dd, J ) 1.8, 8.5 Hz, 1H, H20), 8.03
(d, J ) 1.7 Hz, 1H, H17); 13C NMR (CD3OD-CDCl3) δ 22.0,
28.3, 37.7, 55.7, 57.3, 57.6, 64.7, 70.0, 81.0, 113.4, 115.1, 115.3,
117.0, 118.8, 121.1, 125.6, 126.2, 130.2, 134.3, 136.4, 138.1,
140.1, 142.9, 149.0, 155.2, 158.4, 159.6, 159.9, 169.4, 170.5;
FABMS m/ z 657 (M + Na+), 635 (M + H+); HRMS (CI) m/ z
635.2745 (C33H38N4O9 + H+ requires 635.2717); Selected NOES
(CD3CN, 400 MHz, 313 K) H17-H15; H20-H14, H11, H15′.
Epi-41. Compound epi-41 was obtained as described for
compound 41: mp 86-88; [R]D -46.4° (c 0.55, CHCl3); IR
(CHCl3) 3700, 3425, 2975, 1713, 1675, 1600, 1531, 1488 cm-1
;
1H NMR (CD3CN, 400 MHz, 323K) δ 1.28 (d, J ) 6.0 Hz, 6H,
Me2CH), 1.48 (s, 9H, OBut), 2.86 (t, J ) 12.4 Hz, 1H, H15),
2.89 (m, 1H, OH), 3.24 (dd, J ) 5.3, 12.4 Hz, 1H, H15′), 3.65-
3.83 (m, 2H, H22), 4.47 (m, 1H, H14), 4.59 (septet, J ) 6.0
Hz, 1H, Me2CH), 4.75 (m, 1H, H8), 5.28 (d, J ) 8.5 Hz, 1H,
H11), 6.09 (t, J ) 1.2 Hz, 1H, H21), 6.8-7.2 (m, 10H, aromatics
+ NH), 7.38 (t, J ) 7.9 Hz, 1H, H5), 7.73 (dd, J ) 2.2, 8.4 Hz,
1H, H20), 7.78 (d, J ) 2.2 Hz, 1H, H17); 13C NMR (CDCl3) δ
22.1, 28.3, 39.0, 54.0, 55.4, 56.4, 63.9, 69.7, 80.1, 112.5, 113.8,
115.3, 116.7, 117.9, 119.8, 125.6, 126.8, 129.9, 130.4, 134.9,
135.6, 138.9, 139.4, 139.6, 143.1, 147.4, 155.4, 158.2, 159.6,
169.9: FABMS m/ z 657 (M + Na+), 635 (M + H+). Anal.
Calcd for C33H38N4O9: C, 62.45; H, 6.04; N, 8.83. Found: C,
62.09; H, 6.32; N, 8.54.
Com p ou n d 42. To a solution of 41 (7.1 mg, 0.012 mmol)
in CH2Cl2 (O.5 mL) was added BCl3 (180 µL, 1M in CH2Cl2,
0.18 mmol) at 0 °C. After being stirred for 1 h at 0 °C, the
reaction was quenched by slow addition of anhydrous MeOH.
The volatile was evaporated, and the residue was dissolved
in MeCN (1 mL) and concentrated HCl (0.1 mL) and was
stirred at rom temperature for 1 h. The volatile was evapo-
rated, and the residue was diluted with 4 mL of water and
extracted with ether to remove the neutral species. The
aqueous solution was then neutralized with phosphate buffer
(pH ) 7) and extracted with CH2Cl2. The combined organic
extracts were washed with brine, dried (Na2SO4), and evapo-
rated to afford compound 42 (5.0 mg, 85%) which was used
without further purification: mp ) 277 °C; [R]D +73.3° (c 0.1,
Com p ou n d Epi-40: [R]D -21.5° (c 0.6, CHCl3); IR (CHCl3)
3425, 2950, 2931, 2856, 2400, 1718, 1679, 1587, 1481 cm-1
;
1H NMR (CDCl3, 400 MHz) δ -0.20 (s, 3H, SiMe), -0.18 (s,
3H, SiMe), 0.19 (s, 6H, SiMe2), 0.73 (s, 9H, But), 0.98 (s, 9H,
But), 1.31 (d, J ) 6.0 Hz, 3H, OCHMe2), 1.32 (d, J ) 6.0 Hz,
3H, OCHMe2), 1.38 (s, 9H, OBut), 3.01 (dd, J ) 6.5, 14.0 Hz,
1H, H15), 3.13 (dd, J ) 6.0, 14.0 Hz, 1H, H15′), 3.64 (dd, J )
4.4, 10.3 Hz, 1H, H22), 3.67 (dd, J ) 4.1, 10.3 Hz, 1H, H22′),
4.41 (m, 1H, H14), 4.51 (septet, J ) 6.0 Hz, 1H, OCHMe2),
4.86 (m, 1H, H8), 5.03 (d, J ) 7.5 Hz, 1H, NHBoc), 5.28 (d, J
) 7.3 Hz, 1H, H11), 6.32 (d, J ) 7.3 Hz, 1H, NH9), 6.7-6.9
(m, 5H, aromatics), 6.90 (d, J ) 7.7 Hz, 1H, aromatic), 7.01
(dd, J ) 8.5, 10.6 Hz, 1H, H19), 7.18 (t, J ) 7.8 Hz, 1H, H5),
7.22 (t, J ) 7.8 Hz, 1H), 7.32 (m, 2H, H20, NH12), 7.82 (dd, J
) 2.2 Hz, 7.0 Hz, 1H, H17); 13C NMR (CDCl3) δ -5.6, -4.2,
18.3, 22.1, 24.9, 25.8, 25.9, 28.3, 37.6, 55.0, 57.5, 65.8, 69.9,
80.6, 114.8, 115.6, 118.5 (d, J ) 21.1 Hz), 118.8, 119.2 (d, J )
15.6 Hz), 119.8, 126.9, 129.5, 130.5, 133.8, 136.7 (d, J ) 9.0
Hz), 139.1, 141.2, 155.5 (d, J ) 264.2 Hz), 164.6, 168.7, 169.6;
FABMS m/ z 883 (M + H+). Anal. Calcd for C45H67FN4Si2O9:
C, 61.20; H, 7.65; N, 6.34. Found: C, 61.01; H, 7.93; N, 6.42
Com p ou n d 41. A solution of tripeptide 40 (280 mg, 0.32
mmol) and anhydrous CsF (965 mg, 6.4 mmol) in dry DMF
(30 mL) was stirred at room temperature for 15 h. The
reaction mixture was diluted with aqueous NH4Cl, acidified
to pH ) 4, and extracted with CH2Cl2. The combined organic
extracts were washed with brine, dried (Na2SO4), and evapo-
rated. Flash chromatography (SiO2, EtOAc/heptane ) 1/1)
afforded compound 41 (171 mg, 84%): [R]D -49° (c 0.5, CHCl3);
IR (CHCl3) 3450, 3010, 1716, 1682, 1596, 1536, 1490, 1377,
1
CHCl3/CH3OH 20/1); H NMR (CD3OD, 400 MHz) δ 2.95 (dd,
J ) 3.6, 13.5 Hz, 1H, H15), 3.40 (dd, J ) 4.3, 13.5 Hz, 1H,
H15′), 3.79 (dd, J ) 5.3, 11.3 Hz, 1H, H22), 3.84 (dd, J ) 6.6,
11.3 Hz, 1H, H22′), 3.92 (t, J ) 3.9 Hz, 1H, H14), 4.48 (dd, J
) 5.3, 6.6 Hz, 1H, H8), 5.39 (s, 1H, H11), 6.21 (t, J ) 1.9 Hz,
1H, H21), 6.68 (dd, J ) 2.5, 8.0 Hz, 1H, H25), 6.80 (t, J ) 2.0
Hz, 1H, H29), 6.84 (d, J ) 7.8 Hz, 1H, H27), 6.95 (d, J ) 8.0
Hz, 1H, H4), 7.07 (d, J ) 8.5 Hz, 1H, H19), 7.10 (d, J ) 8.0
Hz, 1H, H6), 7.12 (t, J ) 7.9 Hz, 1H, H28), 7.31 (t, J ) 8.0 Hz,
1H, H5), 7.40 (dd, J ) 2.1, 8.5 Hz, 1H, H20), 8.09 (d, J ) 2.1
Hz, 1H, H17); 13C NMR (CD3OD-CDCl3, 50.03 MHz) δ 39.2,
55.8, 57.0, 59.0, 64.8, 113.0, 113.9, 115.5, 116.5, 118.2, 121.6,
125.9, 126.8, 130.1, 135.1, 136.3, 148.7, 157.9, 160.6, 171.6,
173.7; FABMS m/ z 493 (M + H+); HRMS (CI) m/ z 493.1709
(C25H24N4O7 + H+ requires 493.1723).
Com p ou n d 44. To a solution of 42 (8.1 mg, 0.016 mmol),
(3-fluoro-4-nitrophenyl)acetic acid 39 (6.6 mg, 0.033 mmol) in
DMF (1 mL) were added DPPA (8.8 µL) and Et3N (8.0 µL,
1
1357 cm-1; H NMR (CDCl3, 300 MHz) δ 1.28 (d, J ) 6.0 Hz,

9322 J . Org. Chem., Vol. 61, No. 26, 1996
Bois-Choussy et al.
0.057 mmol) at 0 °C. After being stirred for 5 h at room
temperature, the reaction mixture was diluted with ether (50
mL), washed with water and brine, dried, and evaporated.
Purification of crude product by preparative TLC (SiO2, CH2-
Cl2/MeOH ) 10/1) afforded compound 44 (10.4 mg, 94%): mp
) 147 °C; [R]D +37.3° (c 0.05, CH3OH); IR (CHCl3) 3605, 3010,
2995, 2980, 1675, 1606, 1531, 1488, 1463, 1394 cm-1; 1H NMR
(CD3OD, 250 MHz) δ 3.07 (dd, J ) 3.5, 14.1 Hz, 1H, H15),
3.53 (dd, J ) 5.6, 14.1 Hz, 1H, H15′), 3.81 (dd, J ) 5.2, 11.5
Hz, 1H, H22), 3.84 (d, J ) 14.8 Hz, 1H, H31), 3.92 (d, J )
14.8 Hz, 1H, H31′), 3.95 (m, 1H, H22′), 4.42 (dd, J ) 5.4 Hz,
6.5 Hz, 1H, H8), 4.73 (dd, J ) 3.5, 5.6 Hz, 1H, H14), 5.31 (s,
1H, H11), 6.29 (t, J ) 1.8 Hz, 1H, H21), 6.7-6.8 (m, 3H,
aromatics), 6.96 (br d, J ) 8.5 Hz, 1H, aromatic), 7.0-7.5 (m,
3H, aromatics), 7.13 (d, J ) 8.5 Hz, 1H, H19), 7.33 (t, J ) 8.0
Hz, 1H, H5), 7.35 (dd, J ) 1.2, 8.5 Hz, 1H, H6), 7.44 (dd, J )
1.8, 12.0 Hz, 1H, H37), 7.50 (dd, J ) 2.1, 8.5 Hz, 1H, H20),
8.02 (t, J ) 8.1 Hz, 1H, H36), 8.25 (d, J ) 2.1 Hz, 1H, H17);
13C NMR (CD3OD) δ 36.9, 42.5, 56.4, 57.7, 59.7, 65.0, 114.1,
114.6, 116.0, 117.2, 118.5, 120.1 (d, J ) 20.8 Hz), 122.3, 126.6
(d, J ) 8.2 Hz), 126.9 (d, J ) 14.5 Hz), 135.0, 137.4, 139.4,
142.2, 144.0, 145.3 (d, J ) 3.1 Hz), 149.8, 156.2 (d, J ) 261.4
Hz), 160.9, 170.3, 171.9, 172.4; FABMS m/ z 674 (M + H+)
Com p ou n d 4. A solution of tripeptide 44 (8 mg, 0.012
mmol), anhydrous K2CO3 (16.8 mg, 0.12 mmol), and a catalytic
amount of 18-crown-6 in dry THF (1.5 mL) was stirred at room
temperature for 30 h. The insoluble K2CO3 was removed by
filtration through a short pad of Celite. The filtrate was
evaporated in vacuo and purified directly by flash chromatog-
raphy (SiO2, CH2Cl2/MeOH ) 30/1) to afford compound 4 as a
white solid (6.8 mg, 87%): mp ) 309-312 °C; [R]D + 86.7° (c
0.02, CHCl3/CH3OH ) 10/1); IR (CHCl3) 3600, 3510, 3010,
2990, 1694, 1638, 1612, 1538, 1456, 1400, 1344 cm-1; 1H NMR
(DMSO-d6, 250 MHz) δ 3.13 (dd, J ) 5.3, 14.4 Hz, 1H, H15),
3.53 (dd, J ) 6.2, 14.4 Hz, 1H, H15′), 3.62-3.70 (m, 2H, H22),
3.72 (d, J ) 15.3 Hz, 1H, H31), 3.98 (d, J ) 15.3 Hz, 1H, H31′),
4.45 (br s, 1H, OH), 4.91 (br t, J ) 5.3 Hz, 1H, H8), 4.96-5.02
(m, 1H, H14), 5.49 (br s, 1H, H11), 6.21 (br s, 1H, H21), 7.02
(d, J ) 7.6 Hz, 1H, aromatic), 7.22 (dd, J ) 2.6, 8.1 Hz, 1H,
H4), 7.23-7.28 (m, 2H, aromatics), 7.28 (dd, J ) 2.3, 8.1 Hz,
1H, H6), 7.32 (d, J ) 8.3 Hz, 1H), 7.37-7.45 (m, 3H,
aromatics), 7.49 (t, J ) 8.1 Hz, 1H, H5), 7.59 (br d, J ) 8.2
Hz, 1H, H20), 8.17 (d, J ) 8.3 Hz, 1H, H36), 8.36 (br s, 1H,
H17), 8.62 (br s, 1H, NH9), 8.70 (br s, 1H, NH12); 13C NMR
(DMSO-d6) δ 35.8, 42.1, 54.5, 56.7, 57.5, 63.4, 112.0, 115.1,
118.2, 118.8, 121.2, 123.4, 124.7, 125.5, 125.8, 126.7, 129.3,
130.3, 135.2, 136.5, 141.1, 142.1, 143.2, 147.3, 148.3, 154.9,
159.3, 168.5, 168.8, 168.9; FABMS (Thio/NaCl) m/ z 676
(M + Na+).
Ack n ow led gm en t. One of us (L. Neuville) thanks
“Ministe`re de la Recherche et de l’Enseignement Su-
perieur” for a doctoral fellowship.
Su p p or tin g In for m a tion Ava ila ble: 1H NMR spectra of
selected compounds (14 pages). This material is contained in
libraries on microfiche, immediately follows this article in the
microfilm version of the journal, and can be ordered from the
ACS; see any current masthead page for ordering information.
J O961412M