Carbohydrate-based macrolides prepared via a convergent ring closing metathesis approach: In search for novel antibiotics

Article abstract of DOI:10.1021/jo061929q

(Chemical Equation Presented) An efficient convergent approach has been developed for the construction of novel, nonnatural polysubstituted carbohydrate-based macrolides. A key step in the synthesis is the formation of the macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been screened for biological activity against gram-positive and gram-negative bacteria, yeasts, and molds.

Full text of DOI:10.1021/jo061929q

Carbohydrate-Based Macrolides Prepared via a Convergent Ring
Closing Metathesis Approach: In Search for Novel Antibiotics
Bart Ruttens, Petra Blom, Steven Van Hoof, Idzi Hubrecht, and Johan Van der Eycken*
Laboratory for Organic and Bioorganic Synthesis, Department of Organic Chemistry, Ghent UniVersity,
Krijgslaan 281 (S4), B-9000 Gent, Belgium
Benedikt Sas, Johan Van hemel, and Jan Vandenkerckhove
Kemin Pharma Europe, Atealaan 4H, B-2200 Herentals, Belgium
johan.Vandereycken@ugent.be
ReceiVed September 18, 2006
An efficient convergent approach has been developed for the construction of novel, nonnatural
polysubstituted carbohydrate-based macrolides. A key step in the synthesis is the formation of the
macrocyclic ring via a ring-closing metathesis reaction. The obtained macrolide analogues have been
screened for biological activity against gram-positive and gram-negative bacteria, yeasts, and molds.
Introduction
can circumvent the resistance of mutant microorganisms.5 A
straightforward and intrinsically simple approach is based on
chemical modification of natural macrolides that are accessible
in large quantities from fermentation by microorganisms.
Modifications include acylation of hydroxy groups,6 deacyla-
tion,7 aldehyde or ketone reduction,8 double bond reduction,9
and N-demethylation.10 More fundamental structural changes
require synthesis of macrolide analogues from simple building
blocks, and over the past few years four general approaches
have been developed to control the critical stereochemistry:11
It is assumed that complex natural products in general show
a significantly higher propensity to display biological activity
than small molecules do.1 One of the reasons for this is their
much larger “conformational space”:2 they can adopt a variety
of conformations, thus increasing the chance to efficiently bind
to one or more receptors. Macrolides fall into this category of
large natural product molecules. These fungal metabolites are
characterized by the presence of a macrocyclic lactone ring,
usually linked to one or more neutral sugar moieties and/or
amino sugars, and possess antimicrobial activity.3 However, the
widespread and intensive use of macrolide antibiotics has
accelerated the natural selection of macrolide-resistant patho-
gens.4 Accordingly, there is an increasing demand for second-
generation macrolides, displaying restored activity. Research
indicates that changes in the structure of antimicrobial drugs
(5) Omura, S. Macrolide Antibiotics. Chemistry, Biology and Practice;
Academic Press, Inc.: New York, 1984.
(6) See, e.g.: (a) Tanaka, H.; Moriguchi, I.; Hirono, S.; Omura, S. Chem.
Pharm. Bull. 1985, 33, 2803-2808. (b) Sakakibara, H.; Okekawa, O.;
Fujiwara, T.; Otani, M.; Omura, S. J. Antibiot. 1981, 34, 1001-1010.
(7) Shimauchi, Y.; Hori, K.; Sakamoto, M.; Mutoh, Y.; Fukagawa, Y.;
Hori, S.; Ishikura, T.; Lein, J. J. Antibiot. 1980, 33, 284-292.
(8) See, e.g.: (a) Omura, S.; Miyano, M.; Matsubara, H.; Nakagawa, A.
J. Med. Chem. 1982, 25, 271-275. (b) Omura, S.; Tishler, A.; Nakagawa,
A.; Hironaka, Y.; Hata, T. J. Med. Chem. 1972, 15 (10), 1011-1015.
(9) Adamski, R. J.; Heymann, H.; Geftic, S. G.; Barkulis, S. S. J. Med.
Chem. 1966, 9 (6), 932-934.
(1) Schreiber, S. L. Science 2000, 287, 1964-1969.
(2) Hoffmann, R. W. Angew. Chem., Int. Ed. Engl. 1992, 31 (9), 1124-
1134.
(3) Woodward, R. B. Angew. Chem. 1957, 69, 50-58.
(4) See, e.g.: (a) Arthur, M.; Brissonnoel, A.; Courvalin, P. J. Antimicrob.
Chemother. 1987, 20 (6), 783-802. (b) O’Hara, K.; Kanda, T.; Ohmiya,
K.; Ebisu, T.; Kono, M. Antimicrob. Agents Chemother. 1989, 33 (8), 1354-
1357. (c) Sutcliffe, J.; TaitKamradt, A.; Wondrack, L. Antimicrob. Agents
Chemother. 1996, 40 (8), 1817-1824. (d) Wondrack, L.; Massa, M.; Yang,
B.V.; Sutcliffe, J. Antimicrob. Agents Chemother. 1996, 40 (4), 992-998.
(e) Neu, H. C. Science 1992, 257, 1064-1073.
(10) Mao, J. C. H.; Putterman, M. J. Mol. Biol. 1969, 44 (2), 347-
361.
(11) (a) Paterson, I.; Mansuri, M. M. Tetrahedron 1985, 41, 3569-3624.
(b) Farina, C.; Gagliardi, S. Macrolide Antibiotics. In Seminars in Organic
Chemistry; XIX Summer School “A Corbella”, Gargnano, Italy, June 20-
24, 1994; Societa` Chimica Italiana, Divisione de Chimica Organica: Milano,
Italy 1994; pp 199-225.
10.1021/jo061929q CCC: $37.00 © 2007 American Chemical Society
Published on Web 06/21/2007
5514
J. Org. Chem. 2007, 72, 5514-5522

Carbohydrate-Based Macrolides
SCHEME 1. Retrosynthetic Analysis
(i) ring-cleavage, where the appropriate stereorelationship of
the asymmetric centers is first secured by using the conforma-
tional bias of a small or medium sized ring, which is then opened
to give an acyclic fragment with the stereocenters correctly
related,12 (ii) exploitation of the existing asymmetric centers
and functionalities of a carbohydrate precursor,13 (iii) stereo-
selective introduction of new asymmetric centers on an acyclic
precursor,14 and (iv) stereoselective introduction of new asym-
metric centers onto an intact macrocyclic precursor, using the
conformational bias of the macrocycle.15 Additional problems
in the total synthesis of macrolide analogues are the macrolac-
tonization step and the stereo- and regiocontrolled attachment
of the appropriate basic or neutral deoxysugars.
We have developed a convergent synthetic approach for the
construction of novel, nonnatural carbohydrate-based macrolide
analogues.16 Our strategy is inspired by the carbohydrate
precursor method to control the stereochemistry of the target
macrolides and basically consists of the following key steps:
(i) the synthesis of a carbohydrate scaffold, (ii) attachment of
an acyclic side chain, and (iii) final formation of the macrocyclic
ring via a ring closing metathesis reaction. Previously, we
reported the synthesis of carbohydrate-based macrolide ana-
logues using simple, commercially available, aliphatic side
chains to construct the macrocyclic ring.17 Their interesting
biological activity inspired us to prepare macrocycles with a
more complex substitution pattern, to better resemble natural
macrolides. We now wish to present the synthesis and biological
activity of such macrolide analogues, consisting of a substituted
macrocyclic ring fused to a carbohydrate scaffold. Functional-
ization of the macrocyclic ring was obtained by incorporation
of a polyfunctional acyclic carbohydrate side chain in our
convergent approach (Scheme 1). To limit the ring size, only
one sugar chain was attached to the scaffold to construct the
ring closing metathesis precursor. This dictated ring size and
the position of the double bond after ring closure.
necessary bias for ring closure.18 Due to their cyclic nature,
imposing a conformational restriction, pyranose and furanose
sugars are ideally suited for this purpose. Moreover, carbohy-
drate substructures often occur in natural macrolides and can
contribute significantly to the biological activity of macrolide
compounds. In addition, the use of polyfunctional carbohydrate
scaffolds not only offers an easy access to structural and
configurational diversity, but also eliminates the need for the
often problematic stereo- and regiocontrolled glycosylation after
macrocyclization.
Starting from commercially available 6 two different scaffolds
3 and 4 were prepared (Scheme 2). The key feature of the
reaction sequence is the application of a 4,6-O-prop-2-enylidene
acetal as a protective group for the C4 and C6 hydroxyl
functions. Selective reductive opening19 of this functionality not
only releases a free hydroxyl group at C4, which can be used
for attachment of the side chain via a carbamate bond, but also
generates an allyl ether at C6 providing one of the double bonds
required for RCM. Scaffolds 3 and 4 lack a glycosidic bond
and should have increased metabolic stability compared to
natural carbohydrates.
Results and Discussion
Since the formation of the macrocyclic ring via a ring-closing
metathesis (RCM) reaction represents the key step in our
approach, one of the synthetic functions of the scaffold is to
keep the side chains in the correct position to provide the
Treatment of 6 with hydrogen bromide in acetic acid led to
selective conversion of the anomeric acetate into a bromide,
providing a good leaving group for Grignard substitution with
phenylmagnesium bromide.20 Reacetylation of the deprotected
hydroxyl groups and subsequent crystallization of the crude
product from 2-propanol furnished 7. Deacetylation finally gave
8 in 66% overall yield starting from 6. The enhanced reactivity
of the anomeric acetate also allowed selective exchange with
thiophenol under acidic conditions, exclusively affording 11 due
(12) See, e.g.: (a) Masamune, S.; Kim, C. U.; Wilson, K. E.; Spessard,
G. O.; Gheorgiou, P. E.; Bates, G. S. J. Am. Chem. Soc. 1975, 97, 3512-
3513. (b) Masamune, S.; Yamamoto, H.; Kamata, S.; Fukuzawa, A. J. Am.
Chem. Soc. 1975, 97, 3513-3515. (c) Masamune, S.; Kamata, K.; Schilling,
W. J. Am. Chem. Soc. 1975, 97, 3515-3516.
(13) See, e.g.: (a) Tatsuta, K.; Anemiya, Y.; Maniwa, S.; Kinoshita, M.
Tetrahedron Lett. 1980, 21, 2837-2840. (b) Tatsuta, K.; Yamanuchi, T.;
Kinoshita, M. Bull. Chem. Soc. Jpn. 1978, 51, 3035-3038. (c) Nicolaou,
K. C.; Seitz, S. P.; Pavia, M. R. J. Am. Chem. Soc. 1981, 103, 1222-1224.
(d) Nicolaou, K. C.; Seitz, S. P.; Pavia, M. R. J. Am. Chem. Soc. 1981,
103, 1224-1226. (e) Nicolaou, K. C.; Pavia, M. R.; Seitz, S. P. Tetrahedron
Lett. 1979, 20, 2327-2330.
(14) See, e.g.: Stu¨rmer, R.; Ritter, K.; Hoffmann, R. W. Angew. Chem.,
Int. Ed. Engl. 1993, 32, 101-103.
(15) See, e.g.: Still, W. C.; Novak, V. J. J. Am. Chem. Soc. 1984, 106,
1148-1149.
(16) Sas, B.; Van der Eycken, J.; Vanhemel, J.; Blom, P.; Vandenker-
ckhove, J.; Ruttens, B. PCT Int. Appl. WO 2002-US32817, 2003.
(17) Blom, P.; Ruttens, B.; Van Hoof, S.; Hubrecht, I.; Van der Eycken,
J.; Sas, B.; Van hemel, J.; Vandenkerckhove, J. J. Org. Chem. 2005, 70
(24), 10109-10112.
(18) See, e.g.: (a) Fu¨rstner, A.; Langemann, K. J. Org. Chem. 1996,
61, 3942-3943. (b) Fu¨rstner, A.; Langemann, K. Synthesis 1997, 792-
803. (c) Fu¨rstner, A. Synlett 1999, 10, 1523-1533. (d) Fu¨rstner, A.;
Ackermann, L.; Gabor, B.; Goddard, R.; Lehmann, C. W.; Mynott, R.;
Stelzer, F.; Thiel, O. R. Chem. Eur. J. 2001, 7 (15), 3236-3253.
(19) (a) Garegg, P. J. Acc. Chem. Res. 1992, 25, 575-580. (b) Garegg,
P. J.; Hultberg, H.; Oscarson, S. J. Chem. Soc., Perkin Trans. 1 1982, 2395-
2397.
(20) Panigot, M. J.; Humphries, K. A.; Curley, R. W., Jr. J. Carbohydr.
Chem. 1994, 13 (2), 303-321.
J. Org. Chem, Vol. 72, No. 15, 2007 5515

Ruttens et al.
SCHEME 2. Synthesis of the Scaffolds
to neighboring group participation (JH1-H2 ) 10.1 Hz).21
Reductive cleavage of the thiophenyl group with freshly
prepared Raney nickel under inert atmosphere,22 followed by
methanolysis of the acetates, led to 1,5-anhydro-D-glucitol 13
in 56% overall yield from 6. Acid-catalyzed protection of the
primary hydroxyl function and the secondary alcohol func-
tion at C4 in 8 and 13 as a 4,6-O-prop-2-enylidene acetal,
subsequent methylation of the two remaining hydroxyl groups
under Williamson conditions, and, finally, regioselective reduc-
tive ring opening of the acetal afforded scaffolds 3 and 4,
respectively.
SCHEME 3. Side Reactions during Formation and
Cleavage of 4,6-O-Prop-2-enylidene Acetals
A strong NOE enhancement of both H4 (δ ) 3.45) and H6ax
(δ ) 3.40) upon irradiation of the acetal proton (δ ) 4.83) was
observed for 10, indicating an axial orientation of the acetal
proton (for numbering of the protons, see Scheme 2, structure
10).23 A similar NOE effect was observed for compound 15,
between the acetal proton (δ ) 4.73) and H4 (δ ) 3.28) and
H6ax (δ ) 3.31), demonstrating also in this case the formation
of the thermodynamically favored epimer. The formation of only
one acetal isomer is remarkable, since a cis/trans mixture has
been reported in related cases.24
1,3-Dioxolanes and 1,3-dioxanes are the most common
protective groups for 1,2- and 1,3-diols and the reaction
conditions for their introduction, cleavage, and regioselective
ring opening are well established.25 However, we observed
unexpected side reactions during formation and reductive
cleavage of 10 and 15 (Scheme 3). These acetals are derived
(21) (a) Rosa, L.; Alfonso, F.-M. J. Org. Chem. 1994, 59, 737-745. (b)
Erbing, B.; Lindberg, B. Acta Chem. Scand. Ser. B 1976, 30, 611-612.
(22) Pettit, G. R.; Van Tamelen, E. E. Org. React. 1962, 12 (5), 356-
529.
(23) Desruet, M.-D.; Morin, C.; Ogier, L. Carbohydr. Res. 1997, 301,
225-229.
(24) Holzapfel, C. W.; Huyser, J. J.; van der Merwe, T. L.; van Heerden,
F. R. Heterocycles 1991, 32 (8), 1445-1450.
from an R,â-unsaturated aldehyde (acrolein), and byproducts
arise from addition of nucleophiles to the activated acetal to
give conjugate addition products, in a reaction similar to the
Michael reaction. Preparation of 14, for example, was disturbed
(25) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic
Synthesis, 3th ed.; John Wiley & Sons, Inc.: New York, 1999; pp 201-
237.
5516 J. Org. Chem., Vol. 72, No. 15, 2007

Carbohydrate-Based Macrolides
SCHEME 4. Synthesis of the Polyfunctionalized Side Chain 5
by the 1,4-addition of methanol, liberated from acrolein dimethyl
acetal in the reaction mixture, to the activated acetal, leading
to the undesired formation of 3-methoxypropylidene acetal 16.
A similar side reaction led to a decreased yield for the
regioselective reductive cleavage of acetals 10 and 15
(Scheme 3). According to the literature, 4,6-O-prop-2-enylidene
acetals derived from glycopyranoses behave in the same way
as 4,6-O-benzylidene acetals when treated with NaCNBH3/HCl/
THF, giving predominantly the 6-O-allyl ethers with a free 4-OH
functionality.19 For enhanced reproducibility, we replaced HCl
with TfOH26 to effect regioselective ring opening of prop-2-
enylidene acetals 10 and 15. These reaction conditions led to
the formation of a significant amount (about 15%) of 6-O-propyl
ethers 17a and 17b, respectively, via 1,4-addition of a hydride
to the activated acetal. Acetylation of both products with Ac2O/
pyridine resulted in a downfield shift of one proton (H4),
confirming the position of the propyl ether at C6. To our
knowledge, these side reactions have not been reported in the
literature before.
Highly functionalized aminopolyol side chains can be pre-
pared from amino alditols. The latter are easily accessible via
reductive amination of commercially available monosaccha-
rides.27 The configuration of the resulting polysubstituted acyclic
side chain is determined by the cyclic precursor, and a diverse
set of side chains can be obtained. As a typical example,
commercially available 1-amino-1-deoxy-D-glucitol hydrochlo-
ride 19 is transformed into side chain 5 (Scheme 4). Conversion
of the amino function into azide 20, applying the procedure of
Wong,28 allowed subsequent selective protection of the primary
and secondary hydroxyl groups. Deprotection of pentaacetate
20, followed by selective silylation of the primary alcohol,
furnished compound 21. Methylation of the remaining free
secondary hydroxyl functions led to intermediate 22, which upon
treatment with TBAF afforded the primary alcohol 23 in nearly
quantitative yield. The double bond required for RCM was
introduced by alkylation of alcohol 23 with allyl bromide. Final
reduction of azide 24 with LiAlH4 regenerated the amine
function required for coupling of the side chain with the scaffold
via a carbamate bond. Thus, side chain building block 5 was
obtained as its hydrochloride salt in 6 steps from 19 in 44%
overall yield.
The efficiency of this general procedure was decreased by
the unexpected 1,2- and 1,3-migration of the TBDPS ether29
during methylation of tetrol 21 under basic conditions. LC-MS
analysis of the isomeric mixture indicated the formation of
approximately 19% 1,2-migration product and about 1% 1,3-
migration product. The desired silyl ether 22 proved to be nearly
inseparable from both migration products, but after deprotection
of the silyl ether a mixture of primary and secondary alcohols
was obtained, with enough structural dissimilarities to allow
separation by flash column chromatography on silica gel.
Next, we examined formation of a carbamate bond between
the amine function of 5 and the secundary alcohol function in
scaffolds 3 and 4 (Scheme 5). DMAP-catalyzed treatment of
scaffold 3 with disuccinimidyl carbonate (DSC) in DMF gave
activated carbonate 25 in high yield.30 Nucleophilic displacement
of the N-hydroxysuccinimidyl leaving group with side chain 5
smoothly provided RCM precursor 26, in 91% yield from
alcohol 3. The macrocyclization reaction of diene 26 with the
first generation Grubbs’ catalyst in CH2Cl2 at room temperature
proceeded as planned. This indicates that key parameters for
RCM, such as the distance between the alkene units and the
polar carbamate, as well as their relative orientation and affinity,
are properly assessed in our strategy and provide the necessary
bias for ring closure.18 As expected, formation of the macro-
cyclic ring produced a mixture of E- and Z-isomers 1a and 1b.
While normal and reversed phase chromatography were inad-
equate to effect good separation, silver nitrate impregnated silica
gel31 gave excellent results, affording pure 1a and 1b in a 3.7/1
ratio. Applying a similar synthetic route, scaffold 4 afforded
pure E- and Z-alkene 2a and 2b, respectively, in a 7.2/1 ratio.
The geometry of the double bond in 1a, 1b, 2a, and 2b was
1
deduced from the vinylic vicinal coupling constants in the H
NMR spectra. For all four compounds, the signals from the
(29) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic
Synthesis, 3rd ed.; John Wiley & Sons, Inc.: New York, 1999, pp 114-
116.
(30) See, e.g.: (a) Azumaya, I.; Niwa, T.; Kotani, M.; Iimori, T.; Ikegami,
S. Tetrahedron Lett. 1999, 40 (25), 4683-4686. (b) Fernandez-Forner, D.;
Huerta, J. M.; Ferrer, M.; Casals, G.; Ryder, H.; Giralt, E.; Albericio, F.
Tetrahedron Lett. 2002, 43 (19), 3543-3546. (c) Alsina, J.; Rabanal, F.;
Chiva, C.; Giralt, E.; Albericio, F. Tetrahedron 1998, 54 (34), 10125-
10152. (d) Alsina, J.; Chiva, C.; Ortiz, M.; Rabanal, F.; Giralt, E.; Albericio,
F. Tetrahedron Lett. 1997, 38 (5), 883-886. (e) Ghosh, A. K.; Duong, T.
T.; McKee, S. P.; Thompson, W. J. Tetrahedron Lett. 1992, 33 (20), 2781-
2784. (f) Ogura, H.; Kobayashi, T.; Shimizu, K.; Kawabe, K.; Takeda, K.
Tetrahedron Lett. 1979, 20, 4745-4746.
(26) Pohl, N. L.; Kiessling, L. L. Tetrahedron Lett. 1997, 38 (40), 6985-
6988.
(27) Yoshida, T.; Lee, Y. C. Carbohydr. Res. 1994, 251, 175-186.
(28) Alper, P. B.; Hung, S.-C.; Wong, C.-H. Tetrahedron Lett. 1996, 37
(34), 6029-6032.
(31) Stahl, E. Thin Layer Chromatography, 2nd ed.; Springer-Verlag:
New York, 1969.
J. Org. Chem, Vol. 72, No. 15, 2007 5517

Ruttens et al.
SCHEME 5. Ring Closing Metathesis
vinylic protons were better resolved when the spectrum was
recorded in benzene-d6, but only for 2b was it not possible to
calculate the vinylic vicinal coupling constants from the
spectrum obtained in chloroform-d. Macrolides 1a and 2a
displayed large coupling constants (15-16 Hz), supporting the
E-geometry for the double bond. On the other hand, 1b and 2b
showed significantly smaller coupling constants (11-12 Hz),
indicating the Z-geometry for the double bond. Most signals in
the 1H NMR spectra of the macrolides 1a, 1b, 2a, and 2b were
slightly broadened. A possible explanation for these irregularities
is the occurrence of cis/trans carbamate isomerization. Although
amides and carbamates share common features, the additional
oxygen of the carbamate functionality exerts unique steric and
electronic perturbations. One consequence is that the barriers
for rotation in carbamates are usually 3-4 kcal/mol (about 15-
20%) lower than those in the corresponding amides, provoking
a less pronounced broadening of 1H NMR signals.32 To be able
to attribute the line broadening in the 1H NMR spectra of
macrocycles 1a, 1b, 2a, and 2b to this cis/trans carbamate
isomerization, we had to calculate the free energy of activation
for rotation from the NMR spectra, in order to compare the
value with reported energy barriers for carbamate bond rotation.
Since these calculations are based on the temperature-dependent
fusion of two separate signals from a proton exchanging slowly
between two conformers, we first attempted to increase the
rotational barrier. We envisaged that N-alkylation of the
carbamate would increase the energy of activation for rotation,
slowing down the rate of exchange between different magnetic
environments sufficiently to cause protons of the two conformers
to appear as fully separated signals. Indeed, upon N-methylation
for rotation is now given by eq 2, where the coalescence
temperature Tc is expressed in Kelvin and R is the gas constant.33
k ) π∆ν/21/2 s-1
(1)
∆G# ) RTc[23 + ln(Tc/∆ν)] kJ mol-1
) RTc[23 + 2.3 log(Tc/∆ν)] kJ mol-1 (2)
Although the calculated free energy of activation for rotation
(∆G# ≈ 16 kcal mol-1) is remarkably consistent with the
reported barriers for carbamate bond rotation,33 it should be
emphasized that our calculations are based on strong simplifica-
tions neglecting the unequal population of both environments,
and, therefore, possess only an indicative value. Nevertheless,
1
the results indicate that the distinct line broadening in the H
NMR spectra of compounds 1a, 1b, 2a, and 2b may originate
from cis/trans carbamate isomerization.
The biological activities of macrolides 1a, 1b, 2a, and 2b
toward gram-negative bacteria (E. coli and P. aeruginosa), gram-
positive bacteria (S. aureus, E. faecalis, and C. perfringens),
yeasts (C. albicans and C. neoformans), and molds (A. fumigatus
and T. mentagrophytes) were evaluated applying well-estab-
lished assay techniques34 (see the Supporting Information for
details). None of the screened compounds showed any signifi-
cant activity against bacteria (Table 1). Macrolides 1a, 1b, 2a,
and 2b displayed a moderate activity against C. neoformans
(40-50% growth inhibition at 25 ppm), and 1b, 2a, and 2b to
a lesser extent against A. fumigatus (20-30% growth inhibition
at 25 ppm). Analogues 1a and 1b showed a mild general activity
against yeasts, in particular C. neoformans.
1
of macrolide 1a the H NMR spectrum of the corresponding
carbamate 27a displayed not only enhanced line broadening,
but also the emergence of smaller twin signals. The isolated
position of the twin signals originating from H4 (for numbering,
see Scheme 2, 10) of the scaffold enabled us to do a rough
calculation of the free energy of activation for rotation.
When the two magnetic environments are equally populated,
the rate constant at the coalescence point is given by eq 1, where
∆ν is the frequency separation of the initially sharp lines. NMR
experiments at elevated temperature allowed us to determine
the coalescence temperature Tc. The free energy of activation
In conclusion, we developed a highly convergent and flexible
approach for the construction of polysubstituted macrolide
(33) (a) Williams, D. H.; Fleming, I. Spectroscopic Methods in Organic
Chemistry, 4th ed., revised; McGraw-Hill International (UK) Limited:
Maidenhead, UK, 1989, pp 101-103. (b) Mooney, E. F. Annu. Rep. NMR
Spectrosc., IV 1971, 71-235, Academic Press, London-New York.
(34) Methods are based on the NCCLS (Clinical and Laboratory Standard
Institute) documents M7-A4 (for bacteria), M27-A (for yeasts), and M38-A
(for molds) for the screening of the antimicrobial activity of different
compounds with broth microdilution techniques. An automated Bioscreen
C system was used.
(32) Cox, C.; Lectka, T. J. Org. Chem. 1998, 63, 2426-2427.
5518 J. Org. Chem., Vol. 72, No. 15, 2007

Carbohydrate-Based Macrolides
TABLE 1. Antibacterial and Antifungal Activity of the Macrolide Analogues 1a, 1b, 2a, and 2b34
% of growth at a dose of 25 ppm compared to the negative controla
E.
P.
S.
E.
C.
C.
C.
A.
T.
sample
coli
aeruginosa
aureus
faecalis
perfringens
albicans
neoformans
fumigatus
mentagrophytes
control
1a
1b
2a
2b
100
100
100
100
100
100
88.0
80.3
100
100
100
100
95.6
95.8
95.8
96.1
94.7
94.7
93.7
94.7
91.9
92.4
93.0
93.5
95.0
95.9
95.5
93.7
97.6
99.6
96.5
99.2
54.1
58.4
56.1
51.2
94.0
80.0
69.0
78.0
87.0
92.0
95.0
92.0
94.4
a Average values from five experiments, expressed as the ratio (in %) of the area under the growth curve of the test sample compared to the negative
control.
12.2 Hz), 3.85 (1H, m), 2.09 (3H, s), 2.06 (3H, s), 2.01 (3H, s),
1.80 (3H, s); 13C NMR (125 MHz, CDCl3) δ 170.6, 170.3, 169.4,
168.7, 136.0, 128.8, 128.3, 127.0, 80.1, 75.9, 74.1, 72.4, 68.4, 62.2,
20.6, 20.5, 20.2.
analogues. A diverse set of macrolides, differing in stereochem-
istry and/or in the number of carbon atoms and hydroxyl groups,
is accessible depending on the choice of the carbohydrate
starting materials. The key step in our strategy is the formation
of the macrocyclic ring via a ring-closing metathesis reaction.
All target macrocycles are obtained in good overall yields.
However, in contrast with the unsubstituted carbohydrate-based
macrolides we reported earlier,17 their antibiotic activity is quite
poor.
Synthesis of â-D-Glucopyranosylbenzene (8). Anhydrous K2-
CO3 (2.45 g, 17.70 mmol) was added to a stirred solution of
tetraacetate 7 (28.92 g, 70.81 mmol) in THF (360 mL) and MeOH
(360 mL). Stirring was continued at 25 °C for 18 h. Then, silica
gel (50 g) was added, and the solvent was removed under reduced
pressure. The residue was chromatographed (cyclohexane-acetone-
MeOH 10/10/1) to yield 8 (15.31 g, 90%) as a white foam: Rf
0.19 (cyclohexane-acetone-MeOH 10/10/1); IR (film) 3368, 2919,
2360, 1636, 1496, 1455, 1082, 1042 cm-1; ES-MS (m/z) 258 [M
Experimental Section
Synthesis of 2,3,4,6-Tetra-O-acetyl-â-D-glucopyranosylben-
zene (7). A solution of 6 (12.3 g, 31.50 mmol) in HBr (30% in
HOAc; 50 mL) was stirred for 30 min under argon atmosphere at
25 °C. After evaporation of the solvent under reduced pressure,
residual traces of HOAc were removed by azeotropic evaporation
with toluene (4 × 25 mL), and the residue was dried under high
vacuum. The crude 2,3,4,6-tetra-O-acetyl-â-D-glucopyranosyl bro-
mide was obtained as a yellow solid, and used in the next step
without further purification: Rf 0.46 (cyclohexane-EtOAc 1/1);
IR (film) 2962, 2360, 2342, 1748, 1435, 1369, 1218, 1162, 1112,
1079, 1042 cm-1; ES-MS (m/z) 433 [M + Na]+; 1H NMR
(500 MHz, CDCl3) δ 6.61 (1H, d, J ) 4.0 Hz), 5.56 (1H, t, J )
9.7 Hz), 5.16 (1H, t, J ) 9.7 Hz), 4.84 (1H, dd, J ) 4.0, 10.0 Hz),
4.33 (1H, m), 4.30 (1H, m), 4.13 (1H, dd, J ) 1.5, 12.3 Hz), 2.11
(3H, s), 2.10 (3H, s), 2.05 (3H, s), 2.03 (3H, s); 13C NMR
(125 MHz, CDCl3) δ 170.4, 169.7, 169.6, 169.3, 86.3, 71.9, 70.4,
69.9, 66.9, 60.8, 20.5, 20.5, 20.4, 20.4.
1
+ NH4]+, 263 [M + Na]+; H NMR (500 MHz, CDCl3) δ 7.44
(2H, d, J ) 7.1 Hz), 7.35 (2H, t, J ) 7.6 Hz), 7.30 (1H, m), 4.15
(1H, d, J ) 9.4 Hz), 3.90 (1H, dd, J ) 1.6, 12.1 Hz), 3.72 (1H, dd,
J ) 5.2, 12.0 Hz), 3.51 (1H, t, J ) 8.7 Hz), 3.45 (1H, t, J ) 9.4
Hz), 3.43 (3H, m), 3.40 (1H, t, J ) 9.2 Hz); 13C NMR (125 MHz,
CDCl3) δ 139.3, 127.4, 82.4, 80.7, 78.2, 75.0, 70.4, 61.4.
Synthesis of (R)-4,6-O-Prop-2-enylidene-â-D-glucopyranosyl-
benzene (9). Acrolein dimethyl acetal (2.59 mL, 21.92 mmol) and
CSA (0.42 g, 1.824 mmol) were added to a stirred solution of tetrol
8 (1.752 g, 7.29 mmol) in DMF (12 mL). Stirring was continued
at 25 °C for 24 h. The reaction was quenched with Et3N (305 µL,
2.188 mmol) and the solvent was removed under reduced pressure.
The residue was purified by flash column chromatography (CH2-
Cl2-iPrOH 97/3) to yield 9 (1.77 g, 87%) as a white foam: Rf
0.22 (CH2Cl2-iPrOH: 97/3); [R]20 +13.2 (c 1.01, CHCl3); IR
D
(film) 3407, 2878, 1659, 1103, 1078, 1010 cm-1; EI-MS (m/z) 57
(86), 77 (47), 91 (97), 107 (100), 120 (18), 143 (10), 179 (15), 277
A solution of the crude 2,3,4,6-tetra-O-acetyl-â-D-glucopyranosyl
bromide in Et2O (250 mL) was added to a mechanically stirred
solution of PhMgBr (3 M in Et2O; 100 mL, 300 mmol) in Et2O
(250 mL) at 0 °C. The mixture was allowed to warm to 25 °C, and
stirring was continued for 70 h. The mixture was poured slowly
into H2O (1000 mL), containing HOAc (100 mL), and the organic
and the aqueous layer were separated. The organic phase was
washed with H2O (3 × 250 mL), and the combined aqueous layers
were concentrated under reduced pressure. The residue was
dissolved in pyridine (250 mL), and Ac2O (170 mL) and DMAP
(100 mg, 0.82 mmol) were slowly added at 0 °C. After the mixture
was stirred for 24 h at 25 °C, pyridine and Ac2O were removed by
evaporation under reduced pressure. The residue was dissolved in
Et2O (1500 mL) and washed with saturated NaHCO3 (2 ×
500 mL), 1 M HCl (2 × 500 mL), and H2O (2 × 500 mL). The
organic layer was dried over MgSO4 and filtered, and the solvent
was removed under reduced pressure. The crude product (11.6 g)
was crystallized from 2-propanol, and the mother liquor was purified
by flash column chromatography (CH2Cl2-acetone 99/1). 2,3,
4,6-Tetra-O-acetyl-â-D-glucopyranosylbenzene (7) (combined:
9.391 g, 73%) was obtained as a white solid: Rf 0.42 (cyclohexane-
EtOAc 1/1); mp 149-150 °C; IR (film) 2956, 1753, 1433, 1368,
1
(<1, M+); H NMR (500 MHz, CDCl3) δ 7.38 (4H, br d, J )
4.4 Hz), 7.34 (1H, m), 5.88 (1H, ddd, J ) 4.6, 10.7, 17.4 Hz),
5.53 (1H, dt, J ) 1.2, 17.4 Hz), 5.35 (1H, dt, J ) 1.1, 10.7 Hz),
5.04 (1H, d, J ) 4.6 Hz), 4.26 (1H, d, J ) 9.4 Hz), 4.25 (1H, m),
3.87 (1H, t, J ) 8.7 Hz), 3.62 (2H, m), 3.52 (2H, m), 3.05 (1H, br
s), 2.37 (1H, br s); 13C NMR (125 MHz, CDCl3) δ 138.6, 134.2,
129.6, 129.5, 128.3, 120.5, 101.8, 83.5, 81.5, 76.6, 75.6, 71.6, 69.3.
HRMS (EI) calcd for C15H19O5 279.1233, found 279.1225 [M +
H]+.
Synthesis of 2,3-Di-O-methyl-(R)-4,6-O-prop-2-enylidene-â-
D-glucopyranosylbenzene (10). NaH (60% dispersion in mineral
oil; 0.954 g, 23.86 mmol) was added to a stirred solution of diol 9
(1.66 g, 5.97 mmol) in DMF (60 mL) at 0 °C. After the mixture
was stirred at 0 °C for 30 min, MeI (1.86 mL, 29.83 mmol) was
added. The cooling was removed, and stirring was continued at
25 °C for 21 h. The mixture was then poured into H2O (1000 mL),
the two layers were separated, and the water layer was extracted
with Et2O (3 × 500 mL). The combined organic layers were washed
with brine (500 mL), dried over MgSO4, and concentrated under
reduced pressure. The residue was chromatographed (n-pentane-
Et2O 5/1) to afford dimethyl ether 10 (1.56 g, 86%) as a white
1224, 1104, 1036 cm-1; ES-MS (m/z) 431 [M + Na]+; H NMR
solid: Rf 0.21 (n-pentane-Et2O 5/1); mp 68-70 °C; [R]20 -6.5
1
D
(500 MHz, CDCl3) δ 7.39 (5H, m), 5.24 (1H, t, J ) 9.4 Hz), 5.24
(1H, t, J ) 9.8 Hz), 5.14 (1H, t, J ) 9.8 Hz), 4.40 (1H, d, J ) 9.9
Hz), 4.30 (1H, dd, J ) 4.7, 17.2 Hz), 4.16 (1H, dd, J ) 1.5,
(c 1.05, CHCl3); IR (film) 2934, 2890, 2835, 1167, 1102, 1042,
1032, 1002 cm-1; EI-MS (m/z): 88 (58), 99 (22), 121 (100), 185
(11), 207 (34), 306 (<1, M+); 1H NMR (500 MHz, CDCl3) δ 7.30-
J. Org. Chem, Vol. 72, No. 15, 2007 5519

Ruttens et al.
7.40 (5H, m), 5.90 (1H, ddd, J ) 4.0, 10.8, 17.4 Hz), 5.53 (1H, dt,
J ) 1.3, 17.4 Hz), 5.35 (1H, dt, J ) 1.2, 10.8 Hz), 5.04 (1H, d, J
) 4.0), 4.25 (1H, dd, J ) 4.6, 10.4 Hz), 4.22 (1H, d, J ) 9.6 Hz),
3.66 (3H, s), 3.62 (1H, t, J ) 10.2), 3.52 (1H, t, J ) 8.9), 3.48
(1H, m), 3.47 (1H, m), 3.16 (1H, dd, J ) 8.3, 9.4 Hz), 3.04
(3H, s); 13C NMR (125 MHz, CDCl3) δ 139.5, 134.5, 129.3, 128.3,
119.9, 101.2, 86.5, 85.2, 83.2, 82.4, 71.5, 69.4, 61.8, 61.6. HRMS
(EI) calcd for C17H23O5 307.1546, found 307.1539 [M + H]+.
Synthesis of 6-O-Allyl-2,3-di-O-methyl-â-D-glucopyranosyl-
benzene (3). TfOH (2.44 mL, 27.54 mmol) was added cautiously
via a syringe pump (100 µL/minute) to a stirred mixture of activated
molecular sieves (3 Å, 1.6 mm pellets; 1.140 g), NaCNBH3
(1.80 g, 27.16 mmol), and acetal 10 (1.140 g, 3.72 mmol) in THF
(37 mL) at 25 °C. After addition, the mixture was stirred for another
30 min, before being poured into H2O (250 mL). The aqueous phase
was extracted with CH2Cl2 (3 × 250 mL), and the combined organic
fractions were washed with brine (250 mL). The organic layer was
dried over MgSO4 and filtered through a pad of silica gel. The
solvent was removed under reduced pressure, and the residue was
chromatographed (n-pentane-acetone 85/15) to afford 3 (0.735 g,
64%) and 17a (0.169 g, 15%) as colorless oils. Data for 3: Rf 0.20
(n-pentane-acetone 85/15); [R]20D -16.2 (c 1.07, CHCl3); IR (film)
3420, 2976, 2932, 2905, 2867, 2834, 1145, 1088, 1070 cm-1; ES-
MS (m/z) 41 (38), 73 (20), 88 (75), 121 (100), 147 (11), 207 (10),
308 (<1, M+); 1H NMR (500 MHz, CDCl3) δ 7.38 (2H, br d, J )
6.5 Hz), 7.33 (3H, m), 5.89 (1H, ddd, J ) 5.6, 10.4, 17.2 Hz),
5.27 (1H, dd, J ) 1.6, 17.2 Hz), 5.18 (1H, dd, J ) 1.3, 10.4 Hz),
4.14 (1H, d, J ) 9.5 Hz), 4.08 (1H, ddt, J ) 1.3, 5.6, 12.9 Hz),
4.04 (1H, ddt, J ) 1.3, 5.6, 12.9 Hz), 3.76 (1H, dd, J ) 4.9, 10.4
Hz), 3.72 (1H, dd, J ) 4.4, 10.4 Hz), 3.68 (3H, s), 3.66 (1H, dt, J
) 1.9, 9.2 Hz), 3.56 (1H, p, J ) 4.7 Hz), 3.28 (1H, t, J ) 8.9 Hz),
3.08 (1H, t, J ) 9.2 Hz), 2.97 (1H, br d, J ) 1.9 Hz), 2.94 (3H, s);
13C NMR (125 MHz, CDCl3) δ 139.1, 134.4, 128.3, 128.2, 127.5,
117.4, 87.7, 85.9, 81.6, 77.9, 72.7, 72.4, 70.8, 61.1, 60.1. Anal.
Calcd for C17H24O5: C, 66.21; H, 7.84. Found: C, 66.16; H, 7.95.
Data for 17a: Rf 0.24 (n-pentane-acetone 85/15); 1H NMR
(500 MHz, CDCl3) δ 7.28-7.41 (5H, m), 4.14 (1H, d, J ) 9.5
Hz), 3.77 (1H, dd, J ) 4.8, 10.1 Hz), 3.70 (3H, s), 3.67 (2H, m),
3.56 (1H, p, J ) 4.9 Hz), 3.49 (1H, dt, J ) 6.6, 9.4 Hz), 3.45
(1H, dt, J ) 6.6, 9.4 Hz), 3.29 (1H, t, J ) 8.9 Hz), 3.24 (1H, d, J
) 1.4 Hz), 3.09 (1H, t, J ) 9.3 Hz), 2.96 (3H, s), 1.60 (2H, s, J )
7.1 Hz), 0.91 (3H, t, J ) 7.4 Hz); 13C NMR (125 MHz, CDCl3) δ
139.1, 128.3, 128.2, 127.5, 87.6, 85.7, 81.6, 77.3, 73.8, 73.3, 72.0,
61.1, 60.1, 22.8, 10.6. HRMS (EI) calcd for C17H27O5 311.1858,
found 311.1850 [M + H]+.
of freshly prepared Raney nickel W4 (26 g) in absolute EtOH
(100 mL). The mixture was stirred for 30 min at 25 °C, before the
catalyst was removed by filtration through a celite pad. The catalyst
was washed with absolute EtOH (3 × 50 mL) and the filtrate was
concentrated under reduced pressure. The residue was chromato-
graphed (cyclohexane-EtOAc 6/4) to yield 12 (1.608 g, 80%) as
a white solid: Rf 0.25 (cyclohexane-EtOAc 6/4); mp 65-66 °C;
[R]20 +39.1 (c 1.06, CHCl3); IR (film) 1747, 1228, 1103, 1061,
D
1034 cm-1; EI-MS (m/z) 43 (100), 332 (<1, M+); 1H NMR
(500 MHz, CDCl3) δ 5.19 (1H, t, J ) 9.5 Hz), 5.02 (1H, t, J ) 9.7
Hz), 5.00 (1H, ddd, J ) 5.7, 9.5, 10.4 Hz), 4.19 (1H, dd, J ) 4.9,
12.4 Hz), 4.15 (1H, dd, J ) 5.7, 11.3 Hz), 4.12 (1H, dd, J ) 2.1,
12.4 Hz), 3.58 (1H, ddd, J ) 2.2, 4.9, 10.0 Hz), 3.29 (1H, t, J )
11.0 Hz), 2.09 (3H, s), 2.03 (6H, s), 2.02 (3H, s); 13C NMR
(125 MHz, CDCl3) δ 171.6, 171.2, 170.7, 170.4, 77.3, 74.5, 69.8,
69.2, 67.7, 63.0, 21.6, 21.6, 21.5. HRMS (EI) calcd for C14H21O9
333.1186, found 333.1174 [M + H]+.
Synthesis of 6-O-Allyl-1,5-anhydro-2,3-di-O-methyl-D-glucitol
(4). Following the same procedures as for preparation of 3 from 7,
but starting from tetraacetate 12, successive deacetylation, introduc-
tion of the prop-2-enylidene acetal, methylation of the remaining
free hydroxyl groups, and final reductive opening of the acetal
furnished alcohol 4 as an oil: Rf 0.19 (n-pentane-acetone 85/15);
[R]20 +25.6 (c 1.13, CHCl3); IR (film) 3462, 2970, 2937, 2914,
D
2861, 1463, 1357, 1161, 1128, 1084 cm-1; EI-MS (m/z) 41 (86),
71 (100), 87 (57), 101 (33), 201 (<1); 1H NMR (500 MHz, CDCl3)
δ 5.90 (1H, ddt, J ) 5.8, 10.4, 17.2 Hz), 5.27 (1H, dd, J ) 1.5,
17.2 Hz), 5.19 (1H, dd, J ) 1.5, 10.4 Hz), 4.09 (1H, dd, J ) 5.1,
11.2 Hz), 4.03 (2H, m), 3.69 (1H, dd, J ) 3.3, 10.4 Hz), 3.65 (3H,
s), 3.61 (1H, dd, J ) 5.4, 10.4 Hz), 3.45 (3H, s), 3.45 (1H, m),
3.36 (1H, ddd, J ) 3.3, 5.4, 9.2 Hz), 3.29 (1H, ddd, J ) 5.1, 8.8,
11.0 Hz), 3.15 (1H, t, J ) 11.0 Hz), 3.11 (1H, t, J ) 8.8 Hz), 2.72
(1H, d, J ) 2.2 Hz); 13C NMR (125 MHz, CDCl3) δ 134.4, 117.7,
87.0, 79.8, 78.6, 72.7, 70.9, 70.1, 67.6, 60.9, 58.4. Anal. Calcd for
C11H20O5: C, 56.88; H, 8.68. Found: C, 56.66; H, 8.90.
Synthesis of 1-Azido-1-deoxy-2,3,4,5,6-penta-O-acetyl-D-glu-
citol (20). CH2Cl2 (25 mL) was added to a solution of NaN3
(5.98 g, 91.9 mmol) in H2O (15 mL). This heterogeneous mixture
was cooled to 0 °C and stirred vigorously, while (CF3SO2)O
(3.1 mL, 18.38 mmol) was slowly added over 5 min. The mixture
was allowed to stir vigorously for 2 h at 0 °C before both layers
were separated. The aqueous phase was extracted with CH2Cl2
(2 × 12.5 mL), and the combined organic fractions (∼50 mL) were
washed with saturated Na2CO3 (50 mL). The organic phase was
added to a sirred solution of amino glucitol 19 (2.0 g, 9.19 mmol),
anhydrous K2CO3 (1.90 g, 13.79 mmol), and CuSO4‚5H2O (23 mg,
91.9 µmol) in a mixture of H2O (30 mL) and MeOH (60 mL).
More MeOH was added to obtain a homogeneous solution (about
20 mL). The reaction mixture was stirred for 18 h at 25 °C, and
then it was concentrated under reduced pressure (water bath
<50 °C). The residue was dissolved in pyridine (75 mL), and Ac2O
(45 mL) and DMAP (100 mg, 0.82 mmol) were added. This solution
was stirred for 3 h at 25 °C. After evaporation of the solvent under
reduced pressure, residual traces of pyridine and Ac2O were
removed by azeotropic evaporation with toluene (100 mL). The
residue was dissolved in EtOAc (200 mL) and washed with H2O
(3 × 100 mL). The organic phase was dried over MgSO4, filtered,
and concentrated under reduced pressure. The residue was purified
by chromatography (cyclohexane-EtOAc 65/35) to yield azide 20
(3.70 g, 97%) as a white solid: Rf 0.21 (cyclohexane-EtOAc 7/3);
mp 70-71 °C; [R]20D +7.3 (c 1.05, CHCl3); IR (film) 2107, 1748,
1372, 1216, 1033 cm-1; EI-MS (m/z) 43 (100); ES-MS (m/z) 440
[M + Na]+; 1H NMR (500 MHz, CDCl3) δ 5.47 (1H, dd, J ) 3.5,
7.2 Hz), 5.33 (1H, dd, J ) 3.5, 7.7 Hz), 5.08 (1H, ddd, J ) 3.9,
5.3, 7.2 Hz), 5.05 (1H, ddd, J ) 3.2, 5.0, 7.7 Hz), 4.23 (1H, dd, J
) 3.2, 12.5 Hz), 4.12 (1H, dd, J ) 5.0, 12.5 Hz), 3.53 (1H, dd, J
) 3.9, 13.5 Hz), 3.47 (1H, dd, J ) 5.3, 13.5 Hz), 2.13 (3H, s),
2.12 (3H, s), 2.07 (3H, s), 2.07 (3H, s), 2.07 (3H, s); 13C NMR
(125 MHz, CDCl3) δ 170.6, 170.0, 169.9, 169.8, 70.3, 68.6, 68.4,
Synthesis of Phenyl 2,3,4,6-Tetra-O-acetyl-1-thio-â-D-glu-
copyranoside (11). Thiophenol (43.5 mL, 0.423 mol) and SnCl4
(50.0 mL, 0.268 mmol) were added to a stirred solution of 6
(150.0 g, 0.384 mol) in CH2Cl2 (1.65 l) at 0 °C. Stirring was
continued at 0 °C for 15 min, and then at 25 °C for 24 h. The
mixture was diluted with CH2Cl2 (0.5 L), and washed with 1 N
HCl (2 × 2 L), saturated NaHCO3 (2 × 2 L) and brine (2 × 2 L).
The organic layer was dried over MgSO4 and filtered, and the
solvent was removed under reduced pressure. The crude product
was purified by crystallization from n-pentane-CH2Cl2 to yield
phenyl 2,3,4,6-tetra-O-acetyl-1-thio-â-D-glucopyranoside (11) (131.2
g, 78%) as a white solid: Rf 0.31 (n-hexane-EtOAc 6/4); mp 113-
114 °C; [R]20D -100.9 (c 1.12, CHCl3); IR (film) 1749, 1477, 1437,
1
1369, 1226, 1087, 1036 cm-1; ES-MS (m/z) 463 [M + Na]+; H
NMR (500 MHz, CDCl3) δ 7.49 (2H, m), 7.31 (3H, m), 5.22 (1H,
t, J ) 9.4 Hz), 5.04 (1H, t, J ) 9.8 Hz), 4.97 (1H, t, J ) 9.7 Hz),
4.70 (1H, d, J ) 10.1 Hz), 4.22 (1H, dd, J ) 5.1, 12.3 Hz), 4.18
(1H, dd, J ) 2.5, 12.3 Hz), 3.73 (1H, ddd, J ) 2.5, 5.1, 10.1 Hz),
2.09 (3H, s), 2.08 (3H, s), 2.01 (3H, s), 1.99 (3H, s); 13C NMR
(125 MHz, CDCl3) δ 170.4, 170.0, 169.3, 169.1, 133.0, 131.6,
128.8, 128.3, 85.7, 75.7, 73.9, 69.9, 68.7, 62.1, 20.6, 20.4. Anal.
Calcd for C20H24O9S: C, 54.54; H, 5.49. Found: C, 54.56; H, 5.01.
Synthesis of 1,5-Anhydro-2,3,4,6-tetra-O-acetyl-D-glucitol (12).
Thioglucoside 11 (2.665 g, 6.05 mmol) was added to a suspension
5520 J. Org. Chem., Vol. 72, No. 15, 2007

Carbohydrate-Based Macrolides
68.4, 61.4, 50.6, 20.8, 20.8, 20.5. HRMS (EI) calcd.for C16H23N3-
NaO10 440.1281, found 440.1271 [M + Na]+.
combined organic fractions were washed with brine (100 mL) and
dried over MgSO4. The residue was purified by chromatography
(cyclohexane-EtOAc: 8/2) to yield allyl ether 24 (1.26 g, 95%)
as an oil: Rf 0.22 (cyclohexane-EtOAc 8/2); [R]20D +6.8 (c 1.13,
CHCl3); IR (film) 2932, 2831, 2100, 1096 cm-1; EI-MS (m/z) 41
Synthesis of 1-Azido-6-O-(tert-butyldiphenylsilyl)-1-deoxy-D-
glucitol (21). Anhydrous K2CO3 (0.30 g, 2.21 mmol) was added
to a stirred solution of pentaacetate 20 (3.69 g, 8.84 mmol) in MeOH
(75 mL). Stirring was continued for 4 h at 25 °C, and the mixture
was concentrated under reduced pressure. The residual traces of
MeOH were removed by azeotropic evaporation with CH3CN
(3 × 20 mL). The residue was dissolved in pyridine (40 mL), and
TBDPS-Cl (2.9 mL, 11.05 mmol) was added. The mixture was
stirred for 33 h at 25 °C, and the solvent was removed by
coevaporation with toluene (40 mL). The crude product was purified
by flash column chromatography (CH2Cl2-MeOH 97/3) to afford
compound 21 (3.72 g, 94%) as an oil: Rf 0.18 (CH2Cl2-MeOH
1
(85), 45 (100), 71 (47), 101 (53); H NMR (500 MHz, CDCl3) δ
5.92 (1H, ddt, J ) 5.7, 10.4, 17.2 Hz), 5.28 (1H, dd, J ) 0.8,
17.2 Hz), 5.19 (1H, dd, J ) 0.8, 10.4 Hz), 4.03 (2H, br d, J ) 5.7
Hz), 3.76 (1H, dd, J ) 2.9, 10.6) Hz, 3.60 (1H, ddd, J ) 3.4, 6.0,
7.5 Hz), 3.51 (6H, s), 3.40-3.54 (5H, m), 3.44 (3H, s), 3.43
(3H, s), 3.37 (1H, dd, J ) 7.5, 13.1); 13C NMR (125 MHz, CDCl3)
δ 134.5, 117.2, 80.7, 79.9, 79.7, 78.7, 72.2, 67.2, 60.3, 59.9, 58.9,
57.3, 51.5. HRMS (EI) calcd for C13H26N3O5 304.1872, found
304.1863 [M + H]+.
97/3); [R]20 -8.5 (c 1.09, CHCl3); IR (film) 3414, 2931, 2891,
Synthesis of 6-O-Allyl-1-amino-1-deoxy-2,3,4,5-tetra-O-meth-
yl-D-glucitol (5). A solution of azide 24 (1.35 g, 4.47 mmol) in
THF (20 mL) was added to a suspension of LiAlH4 (0.255 g,
6.70 mmol) in THF (20 mL) at 0 °C. The reaction mixture was
stirred for 5 h at 0 °C. Carefully, wet Et2O (255 µL), a 15% NaOH
solution (255 µL), and H2O (765 µL), were added consecutively
and the mixture was allowed to warm to 25 °C. The precipitate
was removed by filtration through a cotton plug and washed with
THF (200 mL). The filtrate was concentrated under reduced
pressure, and a solution of the residue in CH2Cl2 (45 mL) was
treated with Et2O, saturated with HCl (5 mL). The solvent was
removed under reduced pressure, and the residue was chromato-
graphed (CH2Cl2-MeOH 7/1) to afford side chain 5 (1.31 g, 93%),
which solidified very slowly upon standing: Rf 0.24 (CH2Cl2-
MeOH 7/1); mp 61-63 °C; [R]20D -25.6 (c 1.07, CHCl3); IR (film)
2984, 2936, 2835, 1094 cm-1; EI-MS (m/z) 41 (28), 45 (24), 71
D
2847, 2104, 1428, 1113 cm-1; EI-MS (m/z) 57 (100), 77 (68), 139
(41), 163 (94), 199 (75), 223 (14); 1H NMR (500 MHz, CDCl3) δ
7.66 (4H, m), 7.45 (2H, m), 7.40 (4H, m), 3.93 (1H, m), 3.83 (4H,
m), 3.74 (1H, m), 3.47 (1H, dd, J ) 7.0, 12.6 Hz), 3.41 (1H, dd,
J ) 4.8, 12.6 Hz), 3.34 (2H, br s), 3.25 (1H, br s), 2.96 (1H, br s),
1.07 (9H, s); 13C NMR (125 MHz, CDCl3) δ 135.6, 132.6, 130.1,
128.0, 74.1, 72.9, 71.6, 69.8, 65.2, 53.6, 26.9, 19.3. HRMS (EI)
calcd for C22H32N3O5Si 446.2111, found 446.2103 [M + H]+.
Synthesis of 1-Azido-6-O-(tert-butyldiphenylsilyl)-1-deoxy-
2,3,4,5-tetra-O-methyl-D-glucitol (22). A solution of tetrol 21
(3.67 g, 8.23 mmol) in DMF (40 mL) was added to a suspension
of NaH (1.67 g, 65.84 mmol) in DMF (40 mL) at 0 °C. MeI (10
mL, 160.6 mmol) was added, and the suspension was stirred for
16 h at 25 °C. The mixture was poured into H2O (1000 mL) and
extracted with toluene (3 × 300 mL). The combined organic
fractions were washed with brine (500 mL) and dried over MgSO4.
The residue was chromatographed (cyclohexane-EtOAc 9/1) to
furnish a mixture (2,84 g, 69%) of migration products. LC-MS
indicated that the mixture contained 80% of the desired compound
22 (2.27 g, 55%): Rf 0.19 (cyclohexane-EtOAc 9/1); [R]20D +1.0
(c 1.06, CHCl3); IR (film) 2932, 2899, 2856, 2834, 2823, 2099,
1428, 1115, 1098 cm-1; EI-MS (m/z) 45 (100), 101 (53), 135 (41),
167 (56), 213 (78), 384 (12), 444 (1); 1H NMR (500 MHz, CDCl3)
δ 7.70 (4H, m), 7.40 (6H, m), 3.91 (1H, dd, J ) 2.8, 11.4 Hz),
3.78 (1H, dd, J ) 4.1, 11.4 Hz), 3.59 (1H, ddd, J ) 3.4, 6.1,
7.5 Hz), 3.56 (1H, dd, J ) 3.0, 7.2 Hz), 3.53 (1H, dd, J ) 3.0, 6.1
Hz), 3.51 (3H, s), 3.48 (3H, s), 3.46 (1H, dd, J ) 3.4, 13.1 Hz),
3.44 (3H, s), 3.38 (1H, dd, J ) 7.5, 13.1 Hz), 3.30 (1H, ddd, J )
2.8, 4.1, 7.2 Hz), 1.07 (9H, s); 13C NMR (125 MHz, CDCl3) δ
136.7, 136.5, 134.4, 134.2, 130.5, 128.6, 128.5, 82.2, 81.7, 80.9,
79.4, 62.4, 61.2, 60.8, 59.8, 58.6, 52.7, 27.8, 20.2. HRMS (EI) calcd
for C26H40N3O5Si 502.2737, found 502.2728 [M + H]+.
1
(13), 101 (100), 247 (<1), 278 (<1, M+); H NMR (500 MHz,
CDCl3) δ 5.92 (1H, ddt, J ) 5.7, 10.4, 17.2 Hz), 5.28 (1H, ddd, J
) 1.5, 3.1, 17.2 Hz), 5.18 (1H, dd, J ) 1.5, 10.4 Hz), 4.03 (1H, dt,
J ) 1.2, 5.7 Hz), 3.90 (1H, ddd, J ) 4.2, 5.7, 8.2 Hz), 3.75 (1H,
dd, J ) 2.9, 10.6 Hz), 3.64 (1H, dd, J ) 2.3, 5.9 Hz), 3.48-3.55
(2H, m), 3.53 (3H, s), 3.52 (3H, s), 3.44 (1H, m), 3.44 (3H, s),
3.43 (3H, s), 3.30 (1H, dd, J ) 4.2, 13.2 Hz), 3.10 (1H, dd, J )
8.2, 13.2 Hz); 13C NMR (125 MHz, CDCl3) δ 135.4, 118.2, 80.5,
80.4, 79.0, 77.4, 73.2, 68.1, 60.9, 60.6, 59.9, 58.4, 41.2. Anal. Calcd
for C13H28ClNO5: C, 49.75; H, 8.99; N, 4.46. Found: C, 48.28;
H, 9.25; N, 4.31.
Synthesis of Compound 25. DMAP (291 mg, 2.38 mmol) and
DSC (1.83 g, 7.14 mmol) were added to a stirred solution of alcohol
3 (734 mg, 2.38 mmol) in DMF (11.9 mL), and the mixture was
stirred for 27 h at 25 °C. Then, it was poured into H2O (250 mL)
and extracted with Et2O (3 × 250 mL). The combined organic
fractions were washed with brine (250 mL) and dried over MgSO4.
The residue was treated with Et2O, and the precipitate was filtered
off. The filtrate was concentrated under reduced pressure, and the
crude product was purified by flash column chromatography (n-
pentane-acetone 75/25) to yield 25 (997 mg, 93%) as an oil: Rf
Synthesis of 1-Azido-1-deoxy-2,3,4,5-tetra-O-methyl-D-glucitol
(23). A solution of pure 22 (6.58 g, 13.11 mmol) and TBAF (1M
in THF; 19.7 mL, 19.7 mmol) in THF (100 mL) was stirred at
25 °C for 14 h. The mixture was concentrated under reduced
pressure, and the residue was purified by flash column chroma-
tography (Et2O) to afford alcohol 23 (3.43 g, 99%) as a pale yellow
oil: Rf 0.32 (Et2O); [R]20D +20.3 (c 1.07, CHCl3); IR (film) 2936,
2831, 2100, 1092 cm-1; EI-MS (m/z) 45 (100), 75 (55), 89 (40),
0.28 (n-pentane-acetone 75/25); [R]20 +20.3 (c 1.07, CHCl3);
D
IR (film) 1819, 1790, 1743, 1260, 1233, 1200, 1152, 1070, 1045
cm-1; EI-MS (m/z) 41 (29), 88 (35), 121 (100), 449 (<1, M+); 1H
NMR (500 MHz, CDCl3) δ 7.30-7.42 (5H, m), 5.88 (1H, ddt, J
) 5.7, 10.4, 17.2 Hz), 5.26 (1H, ddd, J ) 1.6, 3.1, 17.2 Hz), 5.18
(1H, dd, J ) 1.4, 10.4 Hz), 4.97 (1H, t, J ) 9.7 Hz), 4.15 (1H, d,
J ) 9.5 Hz), 4.06 (1H, ddt, J ) 1.2, 5.7, 12.9 Hz), 3.99 (1H, ddt,
J ) 1.2, 5.7, 12.9 Hz), 3.73 (1H, ddd, J ) 2.7, 4.5, 9.9 Hz), 3.67
(3H, s), 3.66 (1H, dd, J ) 2.7, 11.0 Hz), 3.62 (1H, dd, J ) 4.5,
11.0 Hz), 3.49 (1H, t, J ) 9.1 Hz), 3.17 (1H, t, J ) 9.2 Hz), 3.01
(3H, s), 2.84 (4H, s); 13C NMR (125 MHz, CDCl3) δ 168.3, 151.1,
138.3, 134.4, 128.2, 127.3, 117.4, 85.5, 85.5, 81.5, 78.4, 76.6, 72.6,
68.4, 61.2, 60.3, 25.4. HRMS (EI) calcd for C22H28NO9 450.1764,
found 450.1754 [M + H]+.
1
101 (55), 131 (25), 232 (1); H NMR (500 MHz, CDCl3) δ 3.90
(1H, br dt, J ) 3.5, 12.1 Hz), 3.68 (1H, br ddd, J ) 3.4, 7.6,
12.1 Hz), 3.60 (1H, ddd, J ) 3.4, 5.8, 7.2 Hz), 3.52 (3H, s), 3.51
(3H, s), 3.48 (3H, s), 3.48 (3H, m), 3.43 (3H, s), 3.38 (1H, dd, J )
7.2, 13.1), 3.36 (1H, m), 2.15 (1H, br t, J ) 4.4 Hz); 13C NMR
(125 MHz, CDCl3) δ 81.7, 81.6, 81.1, 79.5, 61.3, 61.1, 60.2, 59.8,
58.2, 52.4. HRMS (EI) calcd for C10H22N3O5 264.1559, found
264.1552 [M + H]+.
Synthesis of 6-O-Allyl-1-azido-1-deoxy-2,3,4,5-tetra-O-methyl-
D-glucitol (24). NaH (0.220 g, 8.74 mmol) and allyl bromide
(756 µL, 8.74 mmol) were added consecutively to a stirred solution
of alcohol 23 (1.15 g, 4.37 mmol) in DMF (20 mL) at 0 °C. The
mixture was allowed to stir for 4 h at 25 °C before it was poured
into H2O (200 mL) and extracted with toluene (3 × 100 mL). The
Synthesis of Compound 26. A solution of 25 (955 mg,
2.13 mmol) in THF (16 mL) was added to a stirred solution of
side chain 5 (735 mg, 2.34 mmol), DMAP (26 mg, 0.213 mmol),
and Et3N (740 µL, 5.31 mmol) in THF (5 mL). The mixture was
J. Org. Chem, Vol. 72, No. 15, 2007 5521

Ruttens et al.
stirred at 25 °C for 4 h, and the solvent was removed under reduced
pressure. The residue was chromatographed (CH2Cl2-MeOH 97.5/
2.5) to afford compound 26 (1.27 g, 98%) as a pale yellow oil: Rf
0.20 (CH2Cl2-MeOH 97.5/2.5); [R]20D -20.9 (c 1.00, CHCl3); IR
(film) 2976, 2934, 2899, 2832, 1728, 1531, 1245, 1098, 1066, 1028
cm-1; EI-MS (m/z) 41 (89), 45 (89), 71 (44), 88 (91), 121 (100),
147 (11), 611 (<1, M+); 1H NMR (500 MHz, CDCl3) δ 7.38 (2H,
br d, J ) 7.0 Hz), 7.33 (2H, br t, J ) 7.0 Hz), 7.29 (1H, br t, J )
7.0 Hz), 5.93 (1H, ddt, J ) 5.7, 10.9, 16.2 Hz), 5.84 (1H, ddt, J )
5.7, 10.9, 16.2 Hz), 5.28 (1H, dd, J ) 1.2, 17.1 Hz), 5.26 (1H, m),
5.22 (1H, dd, J ) 1.4, 17.1 Hz), 5.19 (1H, br d, J ) 9.6 Hz), 5.12
(1H, dd, J ) 1.2, 10.4 Hz), 4.78 (1H, t, J ) 9.7 Hz), 4.13 (1H, d,
J ) 9.5 Hz), 4.04 (2H, br d, J ) 5.7 Hz), 3.98 (2H, m), 3.77 (1H,
dd, J ) 2.7, 10.6 Hz), 3.69 (1H, ddd, J ) 4.5, 7.2, 13.9 Hz), 3.64
(1H, ddd, J ) 2.7, 6.3, 9.4 Hz), 3.42s3.52 (7H, m), 3.57 (3H, s),
3.54 (3H, s), 3.50 (3H, s), 3.49 (3H, s), 3.43 (3H, s), 3.36 (1H, t,
J ) 9.2 Hz), 3.13 (1H, t, J ) 8.8 Hz), 3.12 (1H, m), 2.98 (3H, s);
13C NMR (125 MHz, CDCl3) δ 155.8, 139.0, 134.7, 128.2, 128.1,
127.5, 117.3, 117.1, 86.0, 85.7, 81.6, 81.3, 79.9, 79.7, 79.1, 78.2,
72.6, 72.4, 72.1, 70.1, 67.5, 60.6, 60.6, 60.3, 59.2, 57.5, 41.8. Anal.
Calcd for C31H49NO11: C, 60.87; H, 8.07; N, 2.29. Found: C, 60.85;
H, 8.18; N, 2.34.
59.67; H, 7.77; N, 2.40. Found: C, 59.71; H, 7.73; N, 2.49. Data
for 1b: Rf 0.28 (CH2Cl2-MeOH 96.5/3.5), Rf (AgNO3) 0.18 (CH2-
Cl2-MeOH 96/4); [R]20 +38.7 (c 1.03, CHCl3); IR (film) 2932,
D
2899, 1724, 1243, 1142, 1095, 1066 cm-1; EI-MS (m/z) 41 (35),
45 (85), 71 (68), 88 (70), 101 (100), 134 (37), 147 (14), 187 (20),
552 (2), 583 (<1, M+); ES-MS (m/z) 584 [M + H]+, 606 [M +
Na]+; 1H NMR (500 MHz, CDCl3) δ 7.39 (2H, br d, J ) 7.2 Hz),
7.32 (2H, br t, J ) 7.2 Hz), 7.27 (1H, br t, J ) 7.2 Hz), 5.70 (1H,
dt, J ) 5.0, 11.5 Hz), 5.67 (1H, dt, J ) 5.4, 11.5 Hz), 4.94 (1H,
dd, J ) 2.6, 8.3 Hz), 4.85 (1H, t, J ) 9.5 Hz), 4.25 (1H, dd, J )
5.4, 12.8 Hz), 4.12 (1H, d, J ) 9.4 Hz), 4.10 (1H, dd, J ) 3.9,
12.8 Hz), 4.06 (2H, m), 3.71 (1H, ddd, J ) 2.5, 8.4, 14.0 Hz),
3.66 (1H, dd, J ) 3.9, 10.9 Hz), 3.63 (1H, t, J ) 4.9 Hz), 3.50-
3.60 (4H, m), 3.57 (3H, s), 3.56 (3H, s), 3.52 (3H, s), 3.48 (3H, s),
3.46 (2H, m), 3.42 (3H, s), 3.38 (1H, m), 3.35 (1H, t, J ) 9.3 Hz),
3.29 (1H, ddd, J ) 3.2, 5.6, 13.9 Hz), 3.16 (1H, t, J ) 9.2 Hz),
1
2.98 (3H, s); H NMR (500 MHz, C6D6) δ 7.44 (2H, br d, J )
7.2 Hz), 7.15 (2H, m), 7.10 (1H, br t, J ) 7.2 Hz), 5.79 (1H, p, J
) 5.4 Hz), 5.51 (1H, p, J ) 5.6 Hz), 5.46 (1H, t, J ) 9.8 Hz), 4.77
(1H, br d, J ) 7.1 Hz), 4.51 (1H, br dd, J ) 6.8, 13.4 Hz), 4.18
(1H, br dd, J ) 4.6, 13.4 Hz), 4.13 (1H, d, J ) 9.5 Hz), 3.90 (1H,
br dd, J ) 5.2, 12.6 Hz), 3.78-3.87 (3H, m), 3.76 (1H, dd, J )
2.3, 10.9 Hz), 3.68-3.74 (2H, m), 3.52-3.59 (4H, m), 3.54 (3H,
s), 3.49 (3H, s), 3.47 (1H, m), 3.47 (3H, s), 3.41 (1H, t, J )
9.2 Hz), 3.14 (3H, s), 3.13 (1H, m), 3.13 (3H, s), 3.09 (1H, ddd, J
) 2.3, 4.9, 14.3 Hz), 2.86 (3H, s); 13C NMR (125 MHz, CDCl3) δ
155.6, 138.8, 130.2, 128.4, 128.1, 128.0, 127.5, 85.7, 85.6, 81.5,
80.7, 80.6, 80.2, 80.0, 78.1, 71.6, 68.8, 67.3, 67.3, 61.0, 60.5, 60.3,
60.1, 57.9, 57.0, 39.6. Anal. Calcd for C29H45NO11: C, 59.67; H,
7.77; N, 2.40. Found: C, 59.67; H, 7.72; N, 2.29.
Synthesis of Compound 1. A solution of diene 26 (1.25 g,
2.05 mmol) in dry and degassed CH2Cl2 (25 mL) and a solution of
Grubbs’ first generation catalyst (170 mg, 0.205 mmol) in dry and
degassed CH2Cl2 (10 mL) were added slowly and simultaneously
to stirred dry and degassed CH2Cl2 (375 mL) over a period of 2 h
at 25 °C. The solution was allowed to stir for 3 additional hours
and, then, a fresh solution of Grubbs’ first generation catalyst
(85 mg, 0.103 mmol) in dry and degassed CH2Cl2 (10 mL) was
added slowly. The mixture was stirred for another 24 h, and the
reaction was quenched by addition of DMSO (1.1 mL, 15.4 mmol).
The mixture was exposed to air and stirred for 24 h. The solvent
was removed under reduced pressure, and the dark brown residue
was chromatographed (cyclohexane-acetone 7/3) to yield a mixture
of E-isomer 1a and Z-isomer 1b (1.132 g, 94%). Chromatography
on AgNO3-impregnated silica gel (CH2Cl2-MeOH 96.5/3.5) fol-
lowed by filtration over silica gel to remove traces of AgNO3
afforded pure 1a (891 mg, 74%) as white crystals and pure 1b
(240 mg, 20%) as a foam. Data for 1a: Rf 0.28 (CH2Cl2-MeOH
96.5/3.5), Rf (AgNO3) 0.30 (CH2Cl2-MeOH 96/4); mp 148-
150 °C; [R]20D +30.8 (c 1.02, CHCl3); IR (film) 2976, 2934, 2899,
2856, 2834, 1720, 1703, 1523, 1508, 1458, 1371, 1248, 1142, 1085,
1066, 1028 cm-1; EI-MS (m/z) 41 (38), 45 (92), 71 (73), 88 (75),
101 (100), 134 (40), 147 (15), 187 (22), 552 (3), 583 (<1, M+);
ES-MS (m/z) 584 [M + H]+, 606 [M + Na]+; 1H NMR (500 MHz,
CDCl3) δ 7.39 (2H, br d, J ) 7.2 Hz), 7.33 (2H, br t, J ) 7.2 Hz),
7.29 (1H, br t, J ) 7.2 Hz), 5.72 (1H, dt, J ) 4.8, 15.9 Hz), 5.67
(1H, dt, J ) 5.1, 15.9 Hz), 4.82 (1H, m), 4.79 (1H, t, J ) 9.7 Hz),
4.13 (1H, d, J ) 9.5 Hz), 4.05 (2H, m), 3.92 (2H, m), 3.83 (1H,
dd, J ) 2.3, 6.7 Hz), 3.81 (1H, ddd, J ) 3.1, 8.2, 12.4 Hz), 3.72
(1H, dd, J ) 5.7, 9.8 Hz), 3.55s3.65 (2H, m), 3.59 (3H, s), 3.57
(3H, s), 3.56 (3H, s), 3.43-3.52 (3H, m), 3.46 (3H, s), 3.45 (3H,
s), 3.41 (1H, dd, J ) 4.2, 6.8 Hz), 3.39 (1H, m), 3.35 (1H, t, J )
9.2 Hz), 3.23 (1H, ddd, J ) 3.6, 8.2, 12.6 Hz), 3.16 (1H, t, J )
Synthesis of Compound 27a. NaH (60% dispersion in mineral
oil; 7 mg, 0.172 mmol) was added to a stirred solution of 1a
(52 mg, 0.089 mmol) in DMF (860 µL) at 0 °C. After 5 min, MeI
(27 µL, 0.430 mmol) was added, and the mixture was stirred for
an additional 90 min at 0 °C. The mixture was poured into H2O
(25 mL) and extracted with Et2O (3 × 25 mL). The combined
organic fractions were washed with brine (25 mL) and dried over
MgSO4, and the solvent was removed under reduced pressure. The
residue was chromatographed (n-hexane-acetone 75/25) to yield
compound 27a (53 mg, 99%) as a white foam: Rf 0.24 (n-hexane-
acetone 75/25); [R]20D +24.8 (c 1.00, CHCl3); IR (film) 2934, 2899,
2834, 1704, 1103, 1090 cm-1; EI-MS (m/z) 88 (83), 101 (100),
187 (23), 201 (8), 566 (3), 597 (<1, M+); ES-MS (m/z) 598 [M +
1
H]+; H NMR (500 MHz, DMSO-d6) δ 4.71 (1H, t, J ) 9.5 Hz,
H4 minor rotamer), 4.59 (1H, t, J ) 9.7 Hz, H4 major rotamer);
13C NMR (125 MHz, DMSO-d6) see the Supporting Information.
HRMS (EI) calcd for C30H48NO11 598.3227, found 598.3213
[M + H]+.
Acknowledgment. The authors are greatly indebted to the
“Instituut ter bevordering van Wetenschap en Technologie in
Vlaanderen” (IWT) for a research grant, and to Kemin Pharma
Europe for financial support.
1
9.2 Hz), 2.99 (3H, s); H NMR (500 MHz, C6D6) δ 7.42 (2H, br
d, J ) 7.2 Hz), 7.15 (2H, m), 7.10 (1H, br t, J ) 7.2 Hz), 5.66
(1H, dt, J ) 5.5, 15.6 Hz), 5.56 (1H, dt, J ) 5.0, 15.6 Hz), 5.37
(1H, t, J ) 9.5 Hz), 4.73 (1H, dd, J ) 3.7, 7.9 Hz), 4.14 (1H, d,
J ) 9.5 Hz), 4.06 (1H, dd, J ) 2.4, 6.9 Hz), 3.95 (1H, ddd, J )
3.5, 8.3, 12.5 Hz), 3.88 (1H, dd, J ) 6.5, 9.5 Hz), 3.85 (2H, br d,
J ) 5.1 Hz), 3.79 (1H, m), 3.74 (2H, br d, J ) 3.9 Hz), 3.67 (1H,
m), 3.66 (1H, t, J ) 8.1 Hz), 3.61 (1H, m), 3.54 (3H, s), 3.52 (1H,
m), 3.51 (3H, s), 3.47 (1H, m), 3.45 (3H, s), 3.43 (1H, t, J )
9.3 Hz), 3.23 (3H, s), 3.19 (1H, ddd, J ) 3.6, 8.2, 12.6 Hz), 3.15
(1H, t, J ) 9.2 Hz), 3.08 (3H, s), 2.88 (3H, s); 13C NMR (125
MHz, CDCl3) δ 155.8, 138.7, 129.9, 128.7, 128.2, 128.0, 127.5,
85.7, 85.5, 81.4, 80.2, 79.9, 79.3, 77.1, 72.2, 71.4, 70.6, 69.0, 68.4,
60.5, 60.4, 60.1, 57.6, 57.5, 39.1. Anal. Calcd for C29H45NO11: C,
Supporting Information Available: Synthesis and spectro-
scopic data of compounds 2a, 2b, 13, 14, 15, 16, 17b, 18a, and
18b; 1H and 13C NMR spectra of all new compounds; preparation
of Raney nickel W4; preparation of AgNO3-impregnated silica gel
and TLC plates; full experimental details on screening protocols
and biological activities of macrolide analogues 1a, 1b, 2a, and
2b; and a detailed description of the calculation of the free energy
of activation for rotation including details of the H NMR spectra
recorded at elevated temperatures. This material is available free
of charge via the Internet at http://pubs.acs.org.
1
JO061929Q
5522 J. Org. Chem., Vol. 72, No. 15, 2007