Synthesis of neoglycoconjugates by the desulfurative rearrangement of allylic disulfides

Article abstract of DOI:10.1021/jo8015314

(Chemical Equation Presented) Two series of neoglycosyl donors are prepared on the basis of connection of an allylic disulfide motif to the anomeric center via a simple O-glycosyl linkage or N-glycosyl amide unit. Conjugation of both sets of donors to cysteine in peptides is demonstrated through classical disulfide exchange followed by the phosphine-mediated desulfurative allylic rearrangement resulting in neoglycopeptides characterized by a simple thioether spacer. The conjugation reaction functions in the absence of protecting groups on both the neoglycosyl donor and peptide in aqueous media at room temperature.

Full text of DOI:10.1021/jo8015314

Synthesis of Neoglycoconjugates by the Desulfurative
Rearrangement of Allylic Disulfides
David Crich* and Fan Yang
Department of Chemistry, Wayne State UniVersity, 5101 Cass AVenue, Detroit, Michigan 48202
dcrich@chem.wayne.edu
ReceiVed July 11, 2008
Two series of neoglycosyl donors are prepared on the basis of connection of an allylic disulfide motif to
the anomeric center via a simple O-glycosyl linkage or N-glycosyl amide unit. Conjugation of both sets
of donors to cysteine in peptides is demonstrated through classical disulfide exchange followed by the
phosphine-mediated desulfurative allylic rearrangement resulting in neoglycopeptides characterized by a
simple thioether spacer. The conjugation reaction functions in the absence of protecting groups on both
the neoglycosyl donor and peptide in aqueous media at room temperature.
SCHEME 1. Ligation via the Desulfurative Allylic Disulfide
Rearrangement
Introduction
We have introduced the desulfurative rearrangement of allylic
disulfides (Scheme 1) as a facile means of electrophile-free,
permanent functionalization of thiols suitable for the modifica-
tion of cysteine and other thiols.1 Herein we report on the
extension of this chemistry to the ligation of carbohydrates to
cysteine in peptides and proteins.
The ability to prepare glycosylated peptides and proteins is
critical to the pursuit and advancement of glycomics and glyco-
science.2 The generation of native linkages between oligosaccha-
rides and peptides typically requires the assembly of preglycosy-
lated peptide building blocks into larger peptides, as exemplified
by recent groundbreaking syntheses employing the method of
native chemical ligation,3 whereas the synthesis of neoglycocon-
jugates in principle allows the conjugation of oligosaccharides to
fully assembled peptides and even proteins.4 Among the many
elegant methods devised,5 the disulfide ligation, as applied to
peptides and proteins by the Boons and Davis groups,6 stands out
for the mildness of conditions and broad functional group tolerance.
The impermanence of the disulfide ligation, due to the ease of
reduction and/or scrambling processes, has promoted the search
(2) (a) Paulson, J. C.; Blixt, O.; Collins, B. E. Nature Chem. Biol. 2006, 2,
238–248. (b) Dwek, R. A.; Butters, T. D. Chem. ReV. 2002, 102, 283–284. (c)
Varki, A. Glycobiology 1993, 3, 97–130. (d) Varki, A., Cummings, R., Esko, J.,
Freeze, H., Hart, G., Marth, J., Eds. Essentials of Glycobiology; Cold Spring
Harbor Press: Cold Spring Harbor, 1999. (e) Buskas, T.; Ingale, S.; Boons, G.-
J. Glycobiology 2006, 16, 113R–136R. (f) Werz, D. B.; Seeberger, P. H. Chem.
Biol. 2007, 2, 661–691. (g) Ernst, B., Hart, G. W., Sinay¨, P., Eds. Carbohydrates
in Chemistry and Biology; Wiley-VCH: Weinheim, 2000. (h) Fraser-Reid, B.,
Kuniaki, T., Thiem, J., Eds. Glycoscience: Chemistry and Chemical Biology;
Springer-Verlag: Berlin, 2001. (i) Fukuda, M., Hindsgaul, O., Eds. Molecular
and Cellular Glycobiology; Oxford University Press: Oxford, 2000. (j) Dem-
chenko, A. V., Ed. Frontiers in Modern Carbohydrate Chemistry; American
Chemical Society: Washington, DC, 2007. (k) Davis, B. G. Chem. ReV. 2002,
102, 579–601. (l) Murrey, H. E.; Hsieh-Wilson, L. C. Chem. ReV. 2008, 108,
1708–1731.
(1) (a) Crich, D.; Krishnamurthy, V.; Hutton, T. K. J. Am. Chem. Soc. 2006,
128, 2544–2545. (b) Crich, D.; Zou, Y.; Brebion, F. J. Org. Chem. 2006, 71,
9172–9177. (c) Crich, D.; Krishnamurthy, V.; Brebion, F.; Karatholuvhu, M.;
Subramanian, V.; Hutton, T. K. J. Am. Chem. Soc. 2007, 129, 10282–10294.
(d) Li, Z.; Wang, C.; Fu, Y.; Guo, Q.-X.; Liu, L. J. Org. Chem. 2008, 73, 6127–
6136.
10.1021/jo8015314 CCC: $40.75
Published on Web 08/27/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 7017–7027 7017

Crich and Yang
for methods to convert the disulfide to a simple thioether, which
have so far been marred by a loss of stereochemical integrity of
the cysteine residue involved in the linkage.7 The application of
the desulfurative allylic rearrangement that we describe here
combines the broad functional group compatibility of the disulfide
ligation with the formation of a permanent thioether-type bond,
and the maintenance of stereochemical integrity of the peptide
chain.
bonates as mixtures of stereoisomers at the newly generated
stereogenic center. Selective hydrazinolysis of the thiolcarbonate
gave the corresponding allylic thiols which were not isolated but
immediately converted to the benzothiazolyl disulfides in high yield
(Scheme 2).
Exactly analogous chemistry with a sialosyl chloride gave
an R-sialyl glycoside carrying the allylic disulfide moiety at the
anomeric position (Scheme 3).
Results and Discussion
SCHEME 3. First-Generation Approach Applied to a Sialic
Acid Derivative
In our approach to neoglycoconjugate synthesis, we envisaged
the use of a short spacer, resulting from the ligation reaction itself,
to link the carbohydrate to the peptide. We preferred to accom-
modate the inherent requirement of the desulfurative allylic disulfide
rearrangement for an allylic sulfide through the use of an appropri-
ate tether, rather than attempt incorporation of this functionality
into the saccharide itself to limit the number of chemical manipula-
tions prior to the ligation reaction. To this end, in a first generation
approach, a series of glycosyl bromides were coupled in ꢀ-selective
reactions to cis-butene-1,4-diol (Scheme 2). Subsequent function-
SCHEME 2. First-Generation Approach to Precursor
Synthesis
A more efficient second-generation protocol involved ap-
plication of the allylic thionocarbonate rearrangement to the
(5) (a) Zhu, X. M.; Pachamuthu, K.; Schmidt, R. R. Org. Lett. 2004, 6, 1083–
1085. (b) Pachamuthu, K.; Schmidt, R. R. Chem. ReV. 2006, 106, 160–187. (c)
Doores, K. J.; Gamblin, D. P.; Davis, B. G. Chem. Eur. J. 2006, 12, 656–665.
(d) Peri, F.; Nicotra, F. Chem. Commun 2004, 623–627. (e) Ohnishi, Y.; Ichikawa,
M.; Ichikawa, Y. Biorg. Med. Chem. Lett. 2000, 10, 1289–1291. (f) Jobron, L.;
Hummel, G. Org. Lett. 2000, 2, 2265–2267. (g) Cohen, S. B.; Halcomb, R. L.
Org. Lett. 2001, 3, 405–407. (h) Knapp, S.; Myers, D. S. J. Org. Chem. 2002,
67, 2995–2999. (i) Zhu, X. M.; Schmidt, R. R. Chem. Eur. J. 2004, 10, 875–
887. (j) Thayer, D. A.; Yu, H. N.; Galan, M. C.; Wong, C.-H. Angew. Chem.,
Int. Ed. 2005, 44, 4596–4599. (k) Yang, Y.-Y.; Ficht, S.; Brik, A.; Wong, C.-H.
J. Am. Chem. Soc. 2007, 129, 7690–7701. (l) Ficht, S.; Payne, R. J.; Brik, A.;
Wong, C.-H. Angew. Chem., Int. Ed. 2007, 46, 5975–5979. (m) Ichikawa, Y.;
Matsukawa, Y.; Isobe, M. J. Am. Chem. Soc. 2006, 128, 3934–3938. (n) Ladmiral,
V.; Mantovani, G.; Clarkson, G. J.; Cauet, S.; Irwin, J. L.; Haddleton, D. M.
J. Am. Chem. Soc. 2006, 128, 4823–4830. (o) Hotha, S.; Kashyap, S. J. Org.
Chem. 2006, 71, 364–367. (p) Ichikawa, Y.; Ohara, F.; Kotsuki, H.; Nakano, K.
Org. Lett. 2006, 8, 5009–5012. (q) Wittrock, S.; Becker, T.; Kunz, H. Angew.
Chem., Int. Ed. 2007, 46, 5226–5230. (r) Ni, J.; Song, H.; Wang, Y.; Stamatos,
N. M.; Wang, L.-X. Bioconjugate Chem. 2006, 17, 493–500. (s) Kolomiets, E.;
Johansson, E. M. V.; Renaudet, O.; Darbre, T.; Reymound, J.-L. Org. Lett. 2007,
8, 14656–11468. (t) Samantaray, S.; Marathe, U.; Dasgupta, S.; Nandicoori,
V. K.; Roy, R. P. J. Am. Chem. Soc. 2008, 130, 2132–2133.
(6) (a) Macindoe, W. M.; van Oijen, A. H.; Boons, G.-J. Chem. Commun.
1998, 847–848. (b) Gamblin, D. P.; Garnier, S. J.; Ward, N. J.; Oldham, A. J.;
Fairbanks, A. J.; Davis, B. G. Org. Biomol. Chem. 2003, 1, 3642–3644. (c)
Gamblin, D. P.; Garnier, P.; van Kasteren, S.; Oldham, N. J.; Fairbanks, A. J.;
Davis, B. G. Angew. Chem., Int. Ed. 2004, 43, 828–833. (d) van Kasteren, S. I.;
Kramer, H. B.; Jensen, H. H.; Campbell, S. J.; Kirkpatrick, J.; Oldham, N. J.;
Anthony, D. C.; Davis, B. G. Nature 2007, 446, 1105–1109. (e) Bernardes,
G. J. L.; Chalker, J. M.; Errey, J. C.; Davis, B. G. J. Am. Chem. Soc. 2008, 130,
5052–5053.
alization of the residual alcohol as a thionocarbonate ester was
followed by heating in toluene at reflux to provoke [3,3]-
sigmatropic rearrangement8 and the formation of allylic thiolcar-
(3) (a) Yamamoto, N.; Tanabe, Y.; Okamoto, R.; Dawson, P. E.; Kajihara,
Y. J. Am. Chem. Soc. 2008, 130, 501–510. (b) Krauss, I. J.; Joyce, J. G.;
Finnefrock, A. C.; Song, H. C.; Dudkin, V. Y.; Geng, X.; Warren, D. J.; Chastain,
M.; Shiver, J. W.; Danishefsky, S. J. J. Am. Chem. Soc. 2007, 129, 11042–
11044. (c) Haase, C.; Seitz, O. Top. Curr. Chem. 2007, 267, 1–36.
(4) (a) Stowell, C. P.; Lee, Y. C. AdV. Carbohydr. Chem. Biochem. 1980,
37, 225–281. (b) Lee, Y. C., Lee, R. T., Eds. Neoglycoconjugates:Preparation
and Applications; Academic Press: San Diego, 1994. (c) Roy, R. In Carbohydrate
Chemistry; Boons, G.-J., Ed.; Blackie Academic and Professional: London, 1998;
pp 243-321. (d) Specker, D.; Wittman, V. Top. Curr. Chem. 2007, 267, 65–
108.
7018 J. Org. Chem. Vol. 73, No. 18, 2008

Synthesis of Neoglycoconjugates
mono(tert-butyldimethylsilyl) ether of cis-butene-1,4-diol and
desilylation followed by glycosylation by the trichloroacetimi-
date method9 to intercept the first-generation method at the stage
of the glycosylated thiolcarbonates 4a-c (Scheme 4).10
direct sulfenylation of the released thiol without isolation
(Scheme 6). The optimum synthesis of the free neoglycosyl
donors is therefore the combination of the second-generation
approach to the protected donor (Scheme 3), followed by
saponification and sulfenylation (Scheme 6).
SCHEME 4. Second-Generation Approach
SCHEME 6. Preparation of Unprotected Neoglycosyl
Donors
The ideal approach (third generation) involved direct glyco-
sylation of the known3 hydroxylated allylic disulfide 14,
accessible from 12 by cleavage of the thiolcarbonate and
sulfenylation in the usual manner, with glycosyl donors 13a-c.
Unfortunately, while this approach was successful (Scheme 5),
it provided the desired products in only moderate yield and
resulted in complications in a subsequent step (vide infra).
Conjugation of the fully deprotected neoglycosyl donors 25
and 26 to the model peptide glutathione was achieved without
issue in pH 8.0 phosphate buffer by simply mixing to achieve
sulfenyl transfer and adding triphenylphosphine to bring about
the sigmatropic rearrangement (Table 2). Interestingly, the yields
in the protecting group free reactions conducted in phosphate
buffer (Table 2) are routinely higher than those conducted with
protected neoglycosyl donors in organic solvent mixtures (Table
1), which we attribute to the established facilitation of the
desulfurative allylic disulfide rearrangement in polar solvents1c
at the expense of the background phosphine-mediated disulfide
cleavage reaction.
SCHEME 5. Third-Generation Approach
A second allylic disulfide linker was prepared as set out in
Scheme 7 with a view to mimicking the N-glycosylamide
linkage. Thus, aldol 31 was subjected to the thio-Mitsunobu
reaction12 to give the thioacetate 32. Saponification and sulfe-
nylation then afforded disulfide 33 which was converted to the
free acid 34 by exposure to trifluoroacetic acid.
SCHEME 7. Preparation of an Alternative Linker
With four protected neoglycosyl donors in hand, a series of
couplings were attempted to model cysteine-containing peptides.
These reactions were conducted at room temperature by mixing
the peptide and the neoglycosyl donor in acetonitrile/methanol
(1:1) as solvent and, after the sulfenyl transfer stage was
complete, adding triphenylphosphine to provoke the key rear-
rangement and render the ligation complete. Initial reactions
were conducted with protected peptides before compatibility
with free glutathione was tested in an aqueous medium. In all
cases, the ligation proceeded efficiently, with the products being
obtained in a highly trans-selective manner with respect to the
linker (Table 1).
Deprotection of the neoglycoconjugate donors encountered
several problems owing to the sensitivity of both disulfides11
and allylic thiols8c to basic conditions. Thus, Zemplen-type
cleavage of disulfides 5a-c and 10 gave complex reaction
mixtures from which only low yields of the desired products
could be isolated. Optimal conditions were eventually found
involving a mild saponification at the level of the thiolcarbonates
4b,c and 9, with concomitant removal of the thiolcarbonate and
J. Org. Chem. Vol. 73, No. 18, 2008 7019

Crich and Yang
TABLE 1. Neoglycoconjugate Formation with Protected Donors
Standard peptide coupling reactions then enabled acid 34 to be
affixed to glycosylamines in the complete absence of protecting
groups (Scheme 8). Although the yields for this coupling process
are only moderate at the present time, it possesses the very obvious
7020 J. Org. Chem. Vol. 73, No. 18, 2008

Synthesis of Neoglycoconjugates
TABLE 2. Protecting Group-Free Neoglycoconjugate Preparation
with Glutathione in Phosphate Buffer
reactions were conducted under an atmosphere of dry nitrogen.
Organic extracts were dried over sodium sulfate and concentrated
under aspirator vacuum at room temperature.
General Procedure for the Reaction of Glycosyl Bromides
with cis-But-2-ene-1,4-diol (2a-c, 7).13 cis-But-2-ene-1,4-diol (10
mL, 120 mmol), Ag2CO3 (750 mg, 2.7 mmol), CaSO4 (2 g), and
an iodine crystal were stirred with the exclusion of moisture and
light for 0.5 h at room temperature before a glycosyl bromide
(1a-c) (1.9 mmol) or the sialyl chloride (6) was added. The reaction
mixture was stirred at room temperature for 24 h and then diluted
with dichloromethane (25 mL) and filtered through Celite and the
filtrate washed with water. The solvent was removed by evaporation,
and the mixture was purified by chromatography over silica gel to
afford the glycosides (2a-c and 7).
(Z)-4-Hydroxybut-2-enyl tetra-O-acetyl-ꢀ-D-glucopyranoside (2a):
white solid, eluted from silica gel with hexane/ethyl acetate (2:1)
1
in 84% yield; mp 97 °C; [R]25 -15.3 (c 1.0, CHCl3); H NMR
D
(500 MHz, CDCl3) δ 5.82 (m, 1H), 5.60 (m, 1H), 5.18 (t, J ) 9.5
Hz, 1H), 5.06 (t, J ) 9.5 Hz, 1H), 4.97 (dd, J ) 8.0, J ) 9.5 Hz,
1H), 4.55 (d, J ) 8.0 Hz, 1H), 4.34 (dd, J ) 6.0, J ) 12.5 Hz,
1H), 4.24 (m, 2H), 4.17 (d, J ) 6.5 Hz, 2H), 4.14 (dd, J ) 2.0, J
) 10.0 Hz, 1H), 3.69 (m, 1H), 2.08 (s, 3H), 2.03 (s, 3H), 2.00 (s,
3H), 1.98 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 170.8, 170.3,
169.5, 133.4, 126.7, 99.3, 72.8, 71.8, 71.2, 68.4, 64.3, 62.0, 58.5,
20.8, 20.7, 20.6. Anal. Calcd for C18H26O11: C, 51.33; H, 6.28; N,
2.49. Found: C, 51.22; H, 6.01; N, 2.44.
(Z)-4-Hydroxybut-2-enyl tetra-O-acetyl-ꢀ-D-galactopyranoside
advantages of convergency and the direct provision of neoglycosyl
donors ready for conjugation without the need for further protecting
group manipulation.
(2b): syrup, eluted from silica gel with hexane/ethyl acetate (2:1)
1
in 83% yield; [R]15 -9.6 (c 1.0, CHCl3); H NMR (500 MHz,
D
CDCl3) δ: 5.75 (m, 1H), 5.52 (m, 1H), 5.30 (d, J ) 3.5 Hz, 1H),
5.11 (dd, J ) 8.0, J ) 10.5 Hz, 1H), 4.93 (dd, J ) 3.5, J ) 10.5
Hz, 1H), 4.45 (d, J ) 8.0 Hz, 1H), 4.28 (dd, J ) 7.5, J ) 12.5 Hz,
1H), 4.20 (dd, J ) 7.5, J ) 12.5 Hz, 1H), 4.11-4.02 (m, 1H),
3.86 (t, J ) 6.5 Hz, 1H), 2.07 (s, 3H), 1.98 (s, 6H), 1.89 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 170.5, 170.3, 170.1, 169.6, 133.5,
126.4, 99.6, 70.9, 70.6, 68.7, 67.1, 64.2, 61.4, 58.3, 20.7, 20.64,
20.5; ESIHRMS calcd for C18H26O11Na [M + Na]+ 441.1368, found
441.1361.
SCHEME 8. Preparation of Amide-Based Neoglycosyl
Donors
(Z)-4-Hydroxybut-2-enyl hepta-O-acetyl-ꢀ-D-cellobioside (2c):
white solid, eluted from silica gel with hexane/ethyl acetate (1:3)
Neoglycoconjugate synthesis with donors 36 was conducted
in aqueous buffer and proceeded in excellent yield (Table 3).
1
in 81% yield; mp 171 °C; [R]15 -21.8 (c 1.1, CHCl3); H NMR
D
(500 MHz, CDCl3) δ 5.83 (m, 1H), 5.60 (m, 1H), 5.15 (m, 2H),
5.05 (t, J ) 9.5 Hz, 1H), 5.90 (m, 2H), 4.55-4.50 (m, 3H), 4.35(dd,
J ) 4.5, J ) 12.5 Hz, 1H), 4.31(dd, J ) 6.0, J ) 13.0 Hz, 1H),
4.23(dd, J ) 7.5, J ) 12.5 Hz, 1H), 4.17 (d, J ) 6.5 Hz, 2H),
4.09-4.03 (m, 2H), 3.76 (t, J ) 9.5 Hz, 1H), 3.64 (m, 1H), 3.59
(m, 1H), 2.13 (s, 3H), 2.07 (s, 3H), 2.05 (s, 3H), 2.02 (s, 3H),
2.003 (s, 3H), 1.998 (s, 3H), 1.97 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 170.6, 170.4, 170.2, 169.8, 169.7, 169.3, 169.1, 133.5,
126.6, 100.7, 99.1, 76.4, 72.9, 72.7, 72.4, 71.9, 71.6, 71.5, 67.7,
64.3, 61.8, 61.5, 58.4, 20.9, 20.70, 20.66, 20.5; ESIHRMS calcd
for C30H42O19Na [M + Na]+ 729.2218, found 729.2191.
Experimental Section
General Methods. All reagents were purchased from commercial
sources and used as received, unless otherwise indicated. All
(7) Bernardes, G. J. L.; Grayson, E. J.; Thompson, S.; Chalker, J. M.; Errey,
J. C.; El Oualid, F.; Claridge, T. D. W.; Davis, B. G. Angew. Chem., Int. Ed.
2008, 47, 2244–2247.
(8) (a) Garmaise, D. I.; Uchiyama, A.; McKay, A. F. J. Org. Chem. 1962,
27, 4509–4512. (b) Ferrier, R. J.; Vethaviyasar, N. J. Chem. Soc., Chem.
Commun. 1970, 1385–1387. (c) Hackler, R. E.; Balko, T. W. J. Org. Chem.
1973, 38, 2106–2110. (d) Nakai, T.; Ari-Izumi, A. Tetrahedron Lett. 1976, 17,
2335–2338. (e) Harano, K.; Ohizumi, N.; Hisano, T. Tetrahedron Lett. 1985,
26, 4203–4206. (f) Harano, K.; Taguchi, T. Chem. Pharm. Bull. 1975, 23, 467–
472. (g) Nakai, T.; Mimura, T.; Ari-Izumi, A. Tetrahedron Lett. 1977, 2425–
2428. (h) Ueno, Y.; Sano, H.; Okawara, M. Tetrahedron Lett. 1980, 21, 1767–
1770. (i) Eto, M.; Tajiri, O.; Nakagawa, H.; Harano, K. Tetrahedron 1998, 54,
8009–8014. (j) Overman, L. E.; Roberts, S. W.; Sneddon, H. F. Org. Lett. 2008,
8, 1485–1488.
(9) (a) Schmidt, R. R. In PreparatiVe Carbohydrate Chemistry; Hanessian,
S., Ed.; Dekker: New York, 1997; pp 283-312. (b) Schmidt, R. R.; Jung, K.-H.
In Carbohydrates in Chemistry and Biology; Ernst, B., Hart, G. W., Sinay¨, P.,
Eds.; Wiley-VCH: Weinheim, 2000; Vol. 1, pp 5-59.
(10) The glycosylation reaction was accompanied by partial cleavage of the
O-2 acetate, which was detrimental to the yield of the product. Therefore, an
acetylation step was included in the workup protocol to reinstall any missing
acetates.
(Z)-4-Hydroxybut-2-enyl (methyl 4,7,8,9-tetra-O-acetyl-5-acety-
lamino-3,5-dideoxy-D-glycero-r-D-galacto-non-2-ulopyranosy-
lonate) (7): white solid, eluted from silica gel with ethyl acetate in
1
58% yield; mp 130.1 °C; [R]24D -11.2 (c 1.2, CHCl3); H NMR
(500 MHz, CDCl3) δ 5.74 (m, 1H), 5.57 (m, 1H), 5.44 (m, 1H),
5.30 (dd, J ) 0.5, J ) 8.5 Hz, 1H), 5.25 (dd, J ) 0.5, J ) 9.5 Hz,
1H), 4.83 (m, 1H), 4.34 (m, 1H), 4.20 (m, 1H), 4.12 (dd, J ) 6.5,
J ) 13.5 Hz, 1H), 4.05 (m, 4H), 3.78 (s, 3H), 2.59 (dd, J ) 4.5,
J ) 12.5 Hz, 1H), 2.16 (s, 3H), 2.14 (s, 3H), 2.03 (s, 3H), 2.02 (s,
3H), 1.87 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 171.04, 170.96,
170.5, 170.3, 168.4 (C-1, JC-1,H-3ax ) 5.0 Hz), 131.8, 127.5, 98.4,
72.4, 69.0, 68.4, 67.3, 62.7, 61.1, 58.3, 52.8, 49.4, 38.1, 23.2, 21.2,
20.9, 20.8. Anal. Calcd for C24H35NO14: C, 51.33; H, 6.28; N, 2.49.
Found: C, 51.22; H, 6.01; N, 2.44.
(11) (a) Danehy, J. P.; Elia, V. J. J. Org. Chem. 1972, 37, 369–373. (b)
Happer, D. A. R.; Mitchell, J. W.; Wright, G. J. Aust. J. Chem. 1973, 26, 121–
134. (c) Ichimura, A.; Nosco, D. L.; Deutsch, E. J. Am. Chem. Soc. 1983, 105,
844–850.
(13) Rodriguez, E. B.; Scally, G. D.; Stick, R. V. Aust. J. Chem. 1990, 43,
1391–1405.
(12) Volante, R. P. Tetrahedron Lett. 1981, 22, 3119–3122.
J. Org. Chem. Vol. 73, No. 18, 2008 7021

Crich and Yang
TABLE 3. Amide-Based Neoglycopeptide Synthesis
General Procedure for the Reaction of Hydroxybutenyl Gly-
cosides with Phenyl Thionochloroformate (3a-c, 8). A solution
of phenyl chlorothionocarbonate (158 µL, 1.14 mmol) in dichlo-
romethane (3 mL) was added to a solution of the alcohols 2a-c
(0.38 mmol), pyridine (184 µL, 2.28 mmol), and DMAP (6 mg) in
dichloromethane (2 mL), and the resulting yellow solution was
stirred at room temperature for 5 h. The reaction mixture was poured
into H2O (10 mL) and extracted with dichloromethane (3 × 10
mL). The combined organic phases were dried, filtered, evaporated,
and purified by chromatography over silica gel.
(Z)-4-(Phenyloxythionocarbonyloxy)-2-butenyl tetra-O-acetyl-
ꢀ-D-glucopyranoside (3a): yellow syrup, eluted from silica gel with
hexane/ethyl acetate (1:1) in 96% yield; [R]21D -9.0 (c 1.2, CHCl3);
1H NMR (500 MHz, CDCl3) δ 7.42 (t, J ) 8.0 Hz, 1H), 7.29 (t, J
) 7.5 Hz, 1H), 7.09 (t, J ) 8.0 Hz, 2H), 5.87 (m, 1H), 5.80 (m,
1H), 5.19 (t, J ) 9.5 Hz, 1H), 5.09 (m, 3H), 5.00 (dd, J ) 8.0, J
) 9.5 Hz, 1H), 4.56 (d, J ) 8.0 Hz, 1H), 4.38 (dq, J ) 5.5, J )
13.5 Hz, 2H), 4.25 (dd, J ) 4.5, J ) 12.0 Hz, 1H), 4.15 (dd, J )
2.0, J ) 12.0 Hz, 1H), 3.69 (m, 1H), 2.07 (s, 3H), 2.05 (s, 3H),
2.01 (s, 3H), 1.99 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 194.9,
170.7, 170.3, 169.41, 169.39, 153.4, 130.6, 129.6, 126.7, 126.1,
121.9, 99.5, 72.8, 71.9, 71.2, 69.2, 68.3, 64.6, 61.9, 20.79, 20.75,
20.6; ESIHRMS calcd for C25H30O12SNa [M + Na]+ 577.1356,
found 577.1338.
67.1, 64.6, 61.3, 20.8, 20.7, 20.6; ESIHRMS calcd for
C25H30O12SNa [M + Na]+ 577.1356, found 577.1344.
(Z)-4-(Phenyloxythionocarbonyloxy)-2-butenyl hepta-O-acetyl-
ꢀ-D-cellobioside (3c): yellow syrup, eluted from silica gel with
hexane/ethyl acetate (1:1) in 96% yield; [R]15 -18.1 (c 1.2,
D
1
CHCl3); H NMR (500 MHz, CDCl3) δ 7.42 (t, J ) 8.0 Hz, 2H),
7.30 (m, 1H), 7.09 (m 2H), 5.87 (m, 1H), 5.79 (m, 1H), 5.19-5.03
(m, 5H), 4.91 (m, 2H), 4.54-4.48 (m, 3H), 4.40-4.31(m, 3H),
3.78 (t, J ) 9.5 Hz, 1H), 3.64 (m, 1H), 3.58 (m, 1H), 2.13 (s, 3H),
2.08 (s, 3H), 2.04 (s, 3H), 2.01 (s, 3H), 2.00 (s, 3H), 1.98 (s, 3H),
1.97 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 195.0, 170.5, 170.33,
170.26, 169.8, 169.7, 169.3, 169.1, 153.4, 130.6, 129.6, 126.7,
126.1, 121.9, 100.8, 99.3, 76.4, 72.9, 72.8, 72.5, 72.0, 71.6, 71.4,
69.2, 67.8, 64.6, 61.8, 61.5, 21.0, 20.8, 20.7, 20.6; ESIHRMS calcd
for C37H46O20SNa [M + Na]+ 865.2201, found 865.2173.
(Z)-4-(Phenyloxythionocarbonyloxy)-2-butenyl (methyl 4,7,8,9-
tetra-O-acetyl-5-acetylamino-3,5-dideoxy-D-glycero-r-D-galacto-
non-2-ulopyranosylonate) (8): yellow syrup, eluted from silica gel
with dichloromethane/methanol (10:1) in 99% yield; [R]24D -12.6
(c 1.2, CHCl3); 1H NMR (500 MHz, CDCl3) δ 7.41(d, J ) 8.0 Hz,
2H), 7.29 (d, J ) 8.0 Hz, 1H), 7.09 (d, J ) 8.0 Hz, 2H), 5.79 (m,
1H), 5.43 (m, 1H), 5.32 (dd, J ) 2.0, J ) 8.5 Hz, 1H), 5.24 (d, J
) 9.0 Hz, 1H), 5.14 (dd, J ) 1.5, J ) 6.5 Hz, 2H), 4.85 (m, 1H),
4.41(dd, J ) 5.0, J ) 13.5 Hz, 1H), 4.29 (dd, J ) 2.5, J ) 12.5
Hz, 1H), 4.06 (m, 4H), 3.79 (s, 3H), 2.60 (dd, J ) 4.5, J ) 13.0
Hz, 2H), 2.16 (s, 3H), 2.12 (s, 3H), 2.023 (s, 3H), 2.017 (s, 3H),
1.87 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 194.9, 171.0, 170.7,
170.24, 170.18, 170.1, 168.2, 153.5, 130.3, 129.6, 126.6, 125.5,
121.9, 98.5, 72.5, 69.8, 69.0, 68.3, 67.2, 61.0, 52.9, 49.4, 38.0, 23.2,
21.2, 20.9, 20.8; ESIHRMS calcd for C31H39NO15SNa [M + Na]+
720.1933, found 720.1928.
(Z)-4-(Phenyloxythionocarbonyloxy)-2-butenyl tetra-O-acetyl-
ꢀ-D-galactopyranoside (3b): yellow syrup, eluted from silica gel
with hexane/ethyl acetate (1:1) in 90% yield; [R]15 -3.5 (c 1.5,
D
1
CHCl3); H NMR (500 MHz, CDCl3) δ 7.38 (m, 2H), 7.26 (dt, J
) 1.0, J ) 7.5 Hz, 1H), 7.07 (m, 2H), 5.81 (m, 2H), 5.34 (dd, J )
0.5, J ) 3.5 Hz, 1H), 5.19 (dd, J ) 8.0, J ) 10.5 Hz, 1H), 5.07
(m, 2H), 4.97 (dd, J ) 3.5, J ) 10.5 Hz, 1H), 4.50 (d, J ) 8.0 Hz,
1H), 4.39 (dd, J ) 5.5, J ) 12.5 Hz, 1H), 4.32 (dd, J ) 6.5, J )
12.5 Hz, 1H), 4.12(d, J ) 7.0 Hz, 1H), 3.88 (dt, J ) 1.5, J ) 6.5
General Procedure for the [3,3]-Sigmatropic Rearrangement
Reaction of Allylic Thionocarbonates (4a-c, 9). A solution of 3a-c
or 8 in toluene was heated at reflux for 8-12 h. Evaporation of the
solvent afforded 4a-c or 9 as yellow syrups in quantitative yield.
Hz, 1H), 2.10 (s, 3H), 2.02 (s, 3H), 1.98 (s, 3H), 1.93 (s, 3H); 13
C
NMR (125 MHz, CDCl3) δ 194.9, 170.3, 170.2, 170.1, 169.4, 153.4,
130.7, 129.6, 126.7, 125.9, 121.9, 100.0, 70.9, 70.8, 69.2, 68.7,
7022 J. Org. Chem. Vol. 73, No. 18, 2008

Synthesis of Neoglycoconjugates
2-(Phenyloxycarbonylthioxy)-3-butenyl Tetra-O-acetyl-ꢀ-D-glu-
copyranoside (4a). An approximately 1:1 mixture of diastereomers:
1H NMR (500 MHz, CDCl3) δ 7.38 (m, 2 × 2H), 7.24 (t, J ) 7.5
Hz, 2 × 1H), 7.15 (m, 2 × 2H), 5.90 (m, 2 × 1H), 5.39 (dd, J )
3.5, J ) 17.0 Hz, 2 × 1H), 5.22 (m, 2 × 2H), 5.08 (dt, J ) 3.5,
J ) 10.0 Hz, 2 × 1H), 5.02 (dt, J ) 2.0, J ) 8.0 Hz, 2 × 1H),
4.58 (d, J ) 8.0 Hz, 1H), 4.56 (d, J ) 8.0 Hz, 1H), 4.16 (m, 2 ×
4H), 3.79 (m, 2 × 1H), 3.70 (m, 2 × 1H), 2.07 (s, 3H), 2.06 (s,
3H), 2.05 (s, 3H), 2.04 (s, 3H), 2.018 (s, 3H), 2.017 (s, 3H), 2.003
(s, 3H), 2.000 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 170.7, 170.3,
169.4, 169.3, 169.0, 168.96, 168.92, 168.31, 168.29, 151.1, 133.6,
129.6, 126.3, 121.3, 119.0, 118.9, 101.3, 100.5, 72.7, 72.6, 71.9,
71.8, 71.04, 71.98, 70.5, 68.4, 68.3, 61.9, 61.8, 48.5, 47.9, 20.8,
20.6; ESIHRMS calcd for C25H30O12SNa [M + Na]+ 577.1356,
found 577.1339.
2-(Phenyloxycarbonylthioxy)-3-butenyl Tetra-O-acetyl-ꢀ-D-ga-
lactopyranoside (4b). An approximately 1:1 mixture of diastereo-
mers: 1H NMR (500 MHz, CDCl3) δ 7.38 (m, 2 × 2H), 7.25 (t, J
) 7.5 Hz, 2 × 2H), 7.15 (m, 2 × 2H), 5.92 (m, 2 × 1H), 5.39 (m,
2 × 2H), 5.24 (m, 2 × 2H), 5.02 (m, 2 × 1H), 4.53 (d, J ) 8.5
Hz, 1H), 4.51 (d, J ) 8.5 Hz, 1H), 4.21-4.10 (m, 2 × 4H), 3.91
(m, 2 × 1H), 3.79 (m, 2 × 1H), 2.513 (s, 3H), 2.148 (s, 3H), 2.07
(s, 3H), 2.06 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H), 1.99 (s, 3H), 1.98
(s, 3H); 13C NMR (125 MHz, CDCl3) δ 170.4, 170.3, 170.2, 169.5,
169.4, 168.9, 151.1, 133.8, 133.4, 129.6, 126.3, 121.3, 118.9, 118.8,
101.8, 101.1, 71.7, 70.83, 70.76, 70.5, 68.6, 68.5, 67.0, 61.3, 48.6,
48.0, 20.88, 20.83, 20.7, 20.6; ESIHRMS calcd for C25H30O12SNa
[M + Na]+ 577.1356, found 577.1331.
2-(Phenyloxycarbonylthioxy)-3-butenyl Hepta-O-acetyl-ꢀ-D-cel-
lobioside (4c). An approximately 1:1 mixture of diastereomers: 1H
NMR (500 MHz, CDCl3) δ 7.37 (t, J ) 8.0 Hz, 2 × 2H), 7.24 (t,
J ) 7.5 Hz, 2 × 1H), 7.14 (m 2 × 2H), 5.87 (m, 2 × 1H), 5.36 (d,
J ) 17.5 Hz, 1H), 5.35 (d, J ) 17.5 Hz, 1H), 5.24-5.11 (m, 2 ×
3H), 5.05 (m, 2 × 1H), 4.91 (m, 2 × 2H), 4.54-4.49 (m, 2 ×
3H), 4.35 (dd, J ) 4.5, J ) 12.5 Hz, 2 × 1H), 4.21-4.02 (m, 2 ×
4H), 3.76 (m, 2 × 2H), 3.65 (m, 2 × 1H), 3.59 (m, 2 × 1H), 2.10
(s, 3H), 2.09 (s, 3H), 2.07 (s, 3H), 2.03 (s, 3H), 2.024 (s, 3H),
2.015 (s, 2 × 3H), 2.01 (s, 2 × 3H), 2.00 (s, 2 × 3H), 1.97 (s, 2
× 3H); 13C NMR (125 MHz, CDCl3) δ 170.5, 170.3, 170.2, 169.8,
169.6, 169.5, 169.3, 169.1, 168.92, 168.87, 151.1, 133.7, 133.4,
129.6, 129.3, 121.3, 118.9, 118.8, 101.2, 100.8, 100.3, 72.9, 72.8,
72.34, 72.29, 72.0, 71.7, 71.6, 71.3, 71.2, 70.4, 67.8, 61.74, 61.7,
61.6, 48.4, 47.9, 20.9, 20.74, 20.72, 20.68, 20.6; ESIHRMS calcd
for C37H46O20SNa [M + Na]+ 865.2201, found 865.2164.
2-(Phenyloxycarbonylthioxy)-3-butenyl (Methyl 4,7,8,9-tetra-
O-acetyl-5-acetylamino-3,5-dideoxy-D-glycero-r-D-galacto-non-2-ul-
opyranosylonate) (9). An approximately 1:1 mixture of diastereo-
mers: 1H NMR (500 MHz, CDCl3) δ 7.36 (t, J ) 8.0 Hz, 2 × 2H),
7.22 (m, 2 × 1H), 7.15 (d, J ) 8.0 Hz, 2 × 2H), 5.92 (m, 2 ×
1H), 5.39 (m, 2 × 2H), 5.32 (m, 2 × 1H), 5.21 (m, 2 × 1H), 4.86
(m, 2 × 1H), 4.27 (t, J ) 12.5 Hz, 2 × 1H), 4.15-4.01 (m, 2 ×
6H), 3.80 (s, 3H), 3.78 (s, 3H), 3.58 (m, 2 × 1H), 2.61 (m, 2 ×
1H), 2.12 (s, 2 × 3H), 2.11 (s, 2 × 3H), 2.03 (s, 2 × 3H), 2.01 (s,
2 × 3H), 1.864 (s, 3H), 1.861 (s, 3H); 13C NMR (125 MHz, CDCl3)
δ 171.2, 170.9, 170.45, 170.37, 170.2, 169.0, 168.4, 168.3, 151.4,
134.4, 134.0, 129.7, 129.3, 128.5, 126.4, 121.6, 118.7, 118.6, 98.9,
98.8, 72.8, 69.3, 68.7, 67.5, 66.5, 66.4, 62.6, 62.5, 53.11, 53.07,
49.7, 48.8, 48.5, 38.1, 23.5, 21.3, 21.10, 21.06, 21.0; ESIHRMS
calcd for C31H39NO15SNa [M + Na]+ 720.1933, found 720.1936.
General Procedure for the Conversion of Allylic Thiocarbon-
ates to Allylic Benzothiazolyl Disulfides. The thiocarbonate (0.48
mmol) and NH2NH2 ·H2O (36 µL, 0.72 mmol) were dissolved with
stirring in DMF (3 mL), followed after 2 min by the dropwise
addition of glacial acetic acid (41 µL, 0.72 mmol) at room
temperature over 0.5 h. The resulting solution was added dropwise
to a well-stirred suspension of 2,2′-dithiobis(benzothiazole) (242
mg, 0.72 mmol) in dichloromethane (3 mL) over 15 min, followed
by stirring at room temperature until completion (∼3 h). The solvent
was evaporated, and the residue was taken up in dichloromethane
and washed with water. The combined organic phases were dried,
filtered, evaporated, and purified by chromatography over silica gel.
2-(Benzothiazol-2-yldisulfanyl)-3-enyl tetra-O-acetyl-ꢀ-D-glu-
copyranoside (5a): yellow foam, eluted from silica gel as an
approximately 1:1 mixture of diastereomers with hexane/ethyl
1
acetate (2:1) in 76% yield; H NMR (500 MHz, CDCl3) δ 7.84
(m, 2 × 2H), 7.44 (t, J ) 7.5 Hz, 2 × 1H), 7.35 (t, J ) 7.5 Hz, 2
× 1H), 5.84 (m, 1H), 5.75 (m, 1H), 5.33-5.18 (m, 2 × 3H),
5.10-5.01 (m, 2 × 2H), 4.55 (d, J ) 8.0 Hz, 1H), 4.54 (d, J ) 8.0
Hz, 1H), 4.26-4.17 (m, 2 × 2H), 4.12 (dt, J ) 2.0, J ) 12.0 Hz,
2 × 1H), 3.85-3.75 (m, 2 × 2H), 3.68 (m, 2 × 1H), 2.08 (s, 3H),
2.06 (s, 3H), 2.05 (s, 3H), 2.024 (s, 3H), 2.021 (s, 3H), 2.009 (s,
3H), 2.008 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 172.7, 172.4,
170.1, 170.3, 169.41, 169.35, 155.0, 135.9, 132.6, 132.3, 126.4,
124.7, 122.23, 122.18, 121.2, 120.7, 120.5, 101.1, 100.8, 72.7, 72.6,
72.0, 71.0, 70.3, 70.1, 68.3, 54.2, 20.8, 20.6; ESIHRMS calcd for
C25H29NO10S3Na [M + Na]+ 622.0846, found 622.0851.
2-(Benzothiazol-2-yldisulfanyl)-3-enyl tetra-O-acetyl-ꢀ-D-galac-
topyranoside (5b): yellow foam, eluted from silica gel as an
approximately 1:1 mixture of diastereomers with hexane/ethyl
1
acetate (2:1) in 48% yield; H NMR (500 MHz, CDCl3) δ 7.86
(m, 2 × 1H), 7.82 (d, J ) 8.0 Hz, 2 × 1H), 7.44 (m, 2 × 1H),
7.33 (m, 2 × 1H), 5.85 (m, 1H), 5.76 (m, 1H), 5.39 (2s, 2 × 1H),
5.34-5.22 (m, 2 × 3H), 5.01 (m, 2 × 1H), 4.51 (d, J ) 8.0 Hz,
1H), 4.50 (d, J ) 8.0 Hz, 1H), 4.22 (m, 2 × 1H), 4.19-4.09 (m,
2 × 2H), 3.89 (m, 2 × 1H), 3.85 (m, 2 × 1H), 3.78 (d, J ) 10.0
Hz, 1H), 3.77 (d, J ) 10.0 Hz, 1H), 2.514 (s, 3H), 2.148 (s, 3H),
2.08 (s, 3H), 2.07 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H), 1.99 (s, 2 ×
3H); 13C NMR (125 MHz, CDCl3) δ 172.7, 172.3, 170.4, 170.3,
170.2, 169.5, 169.4, 155.0, 135.9, 132.7, 132.3, 126.38, 126.35,
124.8, 124.7, 122.24, 122.18, 121.2, 120.7, 120.5, 101.6, 101.3,
70.84, 70.79, 70.7, 70.2, 70.1, 68.5, 66.9, 61.2, 54.2, 20.98, 20.95,
20.7, 20.6; ESIHRMS calcd for C25H29NO10S3Na [M + Na]+
622.0846, found 622.0836.
2-(Benzothiazol-2-yldisulfanyl)-3-enyl hepta-O-acetyl-ꢀ-D-cello-
bioside (5c): yellow foam, eluted from silica gel as an approximately
1:1 mixture of diastereomers with hexane/ethyl acetate (1:1) in 50%
yield; 1H NMR (500 MHz, CDCl3) δ 7.84 (m, 2 × 2H), 7.43 (t, J
) 7.5 Hz, 2 × 1H), 7.34 (t, J ) 7.5 Hz, 2 × 1H), 5.83-5.70 (m,
2 × 1H), 5.31-5.22 (m, 2 × 2H), 5.18-5.11 (m, 2 × 2H), 5.06
(m, 2 × 1H), 4.93 (m, 2 × 2H), 4.53-4.47 (m, 2 × 3H), 4.38 (m,
1H), 4.35 (m, 1H), 4.13 (m, 2 × 1H), 4.10-4.02 (m, 2 × 2H),
3.85-3.73 (m, 2 × 3H), 3.65 (m, 2 × 1H), 3.55 (m, 2 × 1H), 2.17
(s, 3H), 2.10 (s, 3H), 2.082 (s, 3H), 2.079 (s, 3H), 2.04 (s, 3H),
2.03 (s, 3H), 2.023 (s, 3H), 2.020 (s, 3H), 2.015 (s, 2 × 3H), 2.00
(s, 2 × 3H), 1.98 (s, 2 × 3H); 13C NMR (125 MHz, CDCl3) δ
172.7, 172.4, 170.5, 170.29, 170.26, 169.8, 169.61, 169.56, 169.3,
169.1, 155.0, 135.9, 132.7, 132.4, 126.3, 124.7, 122.21, 122.18,
121.2, 120.6, 120.5, 100.8, 100.6, 72.9, 72.8, 72.33, 72.26, 72.0,
71.6, 71.3, 70.2, 70.1, 67.8, 61.7, 61.6, 54.24, 54.21, 20.88, 20.83,
20.80, 20.7, 20.6; ESIHRMS calcd for C37H46O18NS3 [M + H]+
888.1877, found 888.1834.
2-(Benzothiazol-2-yldisulfanyl)-3-enyl (methyl 4,7,8,9-tetra-O-
acetyl-5-acetylamino-3,5-dideoxy-D-glycero-r-D-galacto-non-2-ul-
opyranosylonate) (10): yellow foam, eluted from silica gel as an
approximately 1:1 mixture of diastereomers with dichloromethane/
methanol (10:1) in 60% yield; 1H NMR (500 MHz, CDCl3) δ
7.85(dd, J ) 3.0, J ) 8.0 Hz, 2 × 1H), 7.81 (d, J ) 8.0 Hz, 2 ×
1H), 7.42 (t, J ) 8.0 Hz, 2 × 1H), 7.33 (t, J ) 8.0 Hz, 2 × 1H),
5.83 (m, 2 × 1H), 5.40 (m, 2 × 1H), 5.31 (m, 2 × 2H), 5.24 (m,
2 × 1H), 5.19 (m, 2 × 1H), 4.89 (m, 2 × 1H), 4.28(m, 2 × 1H),
4.10 (m, 2 × 4H), 3.79 (s, 3H), 3.76 (s, 3H), 3.68 (m, 1H), 3.59
(m, 1H), 2.61 (m, 2 × 1H), 2.12 (m, 2 × 6H), 2.03 (m, 2 × 6H),
1.98 (t, J ) 12.50 Hz, 2 × 1H), 1.88 (s, 2 × 3H); 13C NMR (125
MHz, CDCl3) δ 171.0, 170.6, 170.3, 170.1, 168.1, 155.1, 135.9,
132.8, 132.6, 126.2, 124.6, 122.1, 121.1, 120.3, 120.2, 98.7, 98.5,
69.0, 68.5, 68.4, 67.2, 65.8, 68.4, 67.2, 65.8, 65.5, 62.4, 54.8, 54.7,
52.9, 49.4, 37.9, 23.2, 21.1, 20.9, 20.8; ESIHRMS calcd for
C31H38N2O19S3Na [M + Na]+ 765.1429, found 765.1423.
J. Org. Chem. Vol. 73, No. 18, 2008 7023

Crich and Yang
2-(Phenoxycarbonylthioxy)-3-butenol (12). A solution of phenyl
chlorothionocarbonate (5 g, 29 mmol) in dichloromethane (3 mL) was
added to a solution of (E)-4-(tert-butyldimethylsiloxy)but-2-en-1-ol14
(1.95 g, 9.65 mmol), pyridine (4.6 mL, 58 mmol), and 4-(dimethy-
lamino)pyridine (236 mg) in dichloromethane (48 mL). The yellow
solution was stirred for 5 h and then was poured into H2O and extracted
with dichloromethane. The combined organic phases were dried,
filtered, evaporated. The residue was taken up in toluene (200 mL)
and heated at reflux for 4 h at room temperature. Evaporation of the
solvent afforded a yellow syrup which was dissolved in dichlo-
romethane/methanol (9:1), and p-TsOH ·H2O (1.87 g, 9.65 mmol) was
added in one portion. On completion, the reaction mixture was poured
into H2O and extracted with dichloromethane. The combined organic
phases were dried, filtered, evaporated, and purified by chromatography
over silica gel, eluting with with hexane/ethyl acetate (2:1), to give
the title compound as a yellow liquid in (1.2 g, 68%): 1H NMR (500
MHz, CDCl3) δ 7.38 (t, J ) 8.0 Hz, 2 × 2H), 7.25 (t, J ) 7.5 Hz, 2
× 1H), 7.16 (d, J ) 8.0 Hz, 2 × 2H), 5.92 (m, 2 × 1H), 5.44 (d, J )
17.0 Hz, 2 × 1H), 5.32 (d, J ) 10.0 Hz, 2 × 1H), 4.14 (m, 2 × 1H),
3.89 (m, 2 × 2H), 1.92 (t, J ) 6.0 Hz, 2 × 1H); 13C NMR (125 MHz,
CDCl3) δ 169.3, 151.3, 133.7, 129.8, 126.5, 121.5, 119.7, 64.6, 51.3;
ESIHRMS calcd for C11H12O3SNa [M + Na]+ 247.0405, found
247.0430.
General Procedure for the Glycosylation of 2-(Phenoxycarbo-
nylthioxy)-3-butenol with Glycosyl Trichloroacetimidates. The
trichloroacetimidate (0.2 mmol), alcohol 12 (0.4 mmol), and
activated 4 Å powdered molecular sieves were mixed in dichlo-
romethane (2 mL) and stirred at room temperature for 0.5 h before
TMSOTf (0.06 mmol) was added at 0 °C. The reaction mixture
was allowed to warm to room temperature and stirred for 2-4 h,
when TLC showed the donor to hae been consumed. 4-(Dimethy-
lamino)pyridine (0.4 mmol) and Ac2O (0.4 mmol) were added at 0
°C and stirring continued for 4 h at room temperature before
saturated aqueous NaHCO3 was added at 0 °C, and the reaction
mixture was filtered and washed with brine. The organic layer was
dried and concentrated under reduced pressure, and the glycosides
were isolated by silica gel column chromatography (hexane/ethyl
acetate from 95:5 to 2:1).
General Procedure for the Glycosylation of 2-(Benzothiazol-2-
yldisulfanyl)but-3-enol with Glycosyl Trichloroacetimidates. The
trichloroacetimidate (0.2 mmol), 2-(benzothiazol-2-yldisulfanyl)but-
3-en-1-ol1c (0.4 mmol), and activated 4 Å powdered molecular
sieves were mixed in dichloromethane (2 mL) and stirred at room
temperature for 0.5 h before Zn(OTf)2 (74 mg, 0.2 mmol) was added
at 0 °C. The reaction mixture was allowed to warm to room
temperature and was stirred for 8-12 h until TLC indicated
consumption of the donor.15 The reaction mixture was quenched
with saturated aqueous NaHCO3 at 0 °C, filtered, and washed with
brine. The organic layer was dried and concentrated under reduced
pressure, and the glycosides were isolated by silica gel column
chromatography (hexane/ethyl acetate from 95:5 to 2:1).
General Procedure for the Ligation of Protected Neoglycosyl
Donors with Protected Peptides. A solution of cysteine containing
peptide (0.05 mmol) and neoglycosyl donor (0.075 mmol) in
methanol/acetonitrile (0.5 mL/0.5 mL) was stirred at room tem-
perature until TLC indicated completion, after which triphenylphos-
phine (39 mg, 0.15 mmol) was added and the reaction mixture was
stirred at room temperature for 10-24 h. The solution was
evaporated and the mixture purified by chromatography eluting with
dichloromethane/methanol (100:1).
1H), 4.92 (m, 1H), 4.76 (d, J ) 8.0 Hz, 1H), 4.73 (m, 1H), 4.30
(m, 2H), 4.16 (m, 3H), 3.98 (d, J ) 5.5 Hz, 2H), 3.88 (m, 1H),
3.73 (s, 6H), 3.40 (m, 2H), 3.21 (dd, J ) 5.0 Hz, J ) 14.0 Hz,
1H), 2.91 (m, 1H), 2.40 (t, J ) 7.5 Hz, 2H), 2.14 (m, 1H), 2.08 (s,
3H), 2.05 (s, 3H), 2.02 (s, 3H), 1.98 (s, 3H), 1.93 (m, 1H), 1.45 (s,
9H); 13C NMR (125 MHz, CDCl3) δ 172.94, 172.90, 171.2, 170.8,
170.6, 170.0, 169.54, 169.46, 155.8, 129.7, 128.8, 99.5, 80.3, 72.8,
71.7, 71.4, 69.1, 68.4, 62.0, 60.4, 52.6, 52.5, 52.44, 52.36, 41.3,
33.6, 32.5, 32.2, 28.9, 28.7, 28.3, 27.8, 21.1, 20.8, 20.7; ESIHRMS
calcd for C35H53N3O18SNa [M + Na]+ 858.2943, found 858.2936.
S-[4-(Tetra-O-acetyl-ꢀ-D-galactopyranosyloxy)-2E-butenyl] N-(tert-
butyloxycarbonyl)-γ-L-Glu-(r-OMe)-L-Cys-Gly-OMe (17): 67%
yield; [R]23D -36.6 (c 0.1, MeOH); 1H NMR (500 MHz, CD3OD)
δ 5.70 (m, 2H), 5.37 (m, 1H), 5.20 (dd, J ) 3.5 Hz, J ) 11.0 Hz,
1H), 5.09 (m, 1H), 4.74 (d, J ) 7.5 Hz, 1H), 4.54 (m, 1H), 4.29
(m, 1H), 4.14 (m, 5H), 3.722 (s, 3H), 3.716 (s, 3H), 3.31 (m, 2H),
2.98 (dd, J ) 5.5 Hz, J ) 14.0 Hz, 1H), 2.69 (m, 1H), 2.39 (t, J
) 7.5 Hz, 2H), 2.14 (s, 3H), 2.13 (m, 1H), 2.06 (s, 3H), 2.04 (s,
3H), 1.94 (s, 3H), 1.93 (m, 1H), 1.44 (s, 9H); 13C NMR (125 MHz,
CD3OD) δ 173.5, 173.2, 171.9, 170.8, 170.7, 170.2, 170.13, 170.10,
170.0, 156.7, 129.6, 128.6, 99.2, 79.3, 71.0, 70.4, 69.1, 68.3, 67.6,
61.3, 53.1, 52.4, 51.4, 51.3, 40.5, 32.6, 31.8, 31.5, 27.3, 27.0, 19.4,
19.3, 19.1; ESIHRMS calcd for C35H53N3O18SNa [M + Na]+
858.2943, found 858.2940.
S-[4-(Hepta-O-acetyl-ꢀ-D-cellobiosyloxy)-2E-butenyl] N-(tert-bu-
tyloxycarbonyl)-γ-L-Glu-(r-OMe)-L-Cys-Gly-OMe (18): 70% yield;
[R]21 -15.4 (c 0.7, CHCl3); 1H NMR (500 MHz, CD3OD) δ
D
5.69-5.61 (2H, m), 5.24-5.16 (m, 2H), 5.00 (t, J ) 9.6 Hz, 1H),
5.09 (m, 1H), 4.80 (t, J ) 8.4 Hz, 2H), 4.70 (dd, J ) 2.4, J ) 8.0
Hz, 1H), 4.61 (dd, J ) 4.0, J ) 8.0 Hz, 1H), 4.53 (m, 2H), 4.39
(m, 1H), 4.26 (m, 1H), 4.14 (m, 3H), 4.04 (dd, J ) 2.0, J ) 12.4
Hz, 1H), 3.97 (s, 2H), 3.89-3.81 (m, 2H), 3.78 (m, 1H), 3.72 (s,
3H), 3.71 (s, 3H), 3.18 (m, 2H), 2.96 (m, 1H), 2.67 (m, 1H), 2.37
(t, J ) 7.4 Hz, 2H), 2.12 (m, 4H), 2.05 (s, 3H), 2.02 (s, 3H), 2.01
(s, 3H), 1.98 (s, 3H), 1.93 (m, 4H), 1.43 (s, 9H); 13C NMR (125
MHz, CD3OD) δ 173.7, 173.3, 171.8, 171.7, 171.2, 171.0, 170.7,
170.4, 170.1, 170.0, 169.8, 156.5, 133.5, 126.1, 100.7, 99.0, 79.5,
76.9, 73.3, 73.1, 72.8, 71.9, 71.8, 71.7, 68.1, 64.1, 62.4, 61.6, 57.5,
55.74, 55.70, 53.3, 51.6, 51.5, 40.8, 40.7, 31.7, 27.6, 27.2, 25.8,
19.8, 19.6, 19.53, 19.5, 19.40, 19.38; ESIHRMS calcd for
C47H69N3O26SNa [M + Na]+ 1146.3788, found 1146.3786.
S-[4-(Tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)-2E-butenyl] N-(tert-
butyloxycarbonyl)-L-Cys-L-Ala-L-Trp-OMe (20): 59% yield; [R]23
D
1
-19.9 (c 0.9, MeOH); H NMR (500 MHz, CD3OD) δ 7.50 (d, J
) 8.0 Hz, 1H), 7.33 (d, J ) 8.0 Hz, 1H), 7.09 (m, 2H), 7.02 (m,
1H), 5.63 (m, 2H), 5.25 (t, J ) 10.0 Hz, 1H), 4.99 (t, J ) 10.0 Hz,
1H), 4.73 (m, 1H), 4.64 (d, J ) 8.0 Hz, 1H), 4.42 (m, 1H), 4.24
(m, 2H), 4.17 (m, 1H), 4.09 (m, 3H), 3.76 (m, 1H), 3.64 (s, 3H),
3.27 (m, 1H), 3.22 (m, 1H), 3.10 (d, J ) 2.5 Hz, 1H), 2.81 (m,
1H), 2.04 (s, 3H), 2.01 (s, 3H), 1.99 (s, 3H), 1.95 (s, 3H), 1.44 (s,
9H), 1.32 (d, J ) 7.0 Hz, 3H); 13C NMR (125 MHz, CD3OD) δ
173.0, 172.2, 171.6, 171.0, 170.3, 169.9, 169.8, 156.3, 136.6, 129.3,
128.5, 127.4, 123.3, 121.1, 118.5, 117.8, 111.0, 109.1, 99.2, 79.5,
72.9, 71.5, 71.3, 68.6, 68.4, 61.7, 60.2, 53.8, 53.4, 51.3, 48.9, 32.7,
32.4, 27.3, 27.1, 19.5, 19.4, 19.3, 19.2, 16.8, 13.1; ESIHRMS calcd
for C41H57N4O16S [M + H]+ 893.3485, found 893.3488.
S-[4-(Tetra-O-acetyl-ꢀ-D-galactopyranosyloxy)-2E-butenyl] N-
(tert-butyloxycarbonyl)-L-Cys-L-Ala-L-Trp-OMe (21): 66% yield;
[R]21D -10.5 (c 1.1, MeOH); 1H NMR (500 MHz, CDCl3) δ 8.61
(br s, 1H), 7.49 (t, J ) 8.0 Hz, 1H), 7.35 (d, J ) 8.0 Hz, 1H), 7.16
(t, J ) 7.5 Hz, 1H), 7.09 (t, J ) 7.5 Hz, 1H), 7.00 (s, 1H), 6.83 (d,
J ) 7.5 Hz, 1H), 6.79 (d, J ) 7.0 Hz, 1H), 5.63 (m, 2H), 5.38 (d,
J ) 3.0 Hz, 1H), 5.32 (d, J ) 7.0 Hz, 1H), 5.23 (m, 1H), 5.13 (dd,
J ) 3.5, J ) 10.5 Hz, 1H), 4.88 (m, 1H), 4.61 (d, J ) 7.5 Hz, 1H),
4.50 (t, J ) 7.2 Hz, 1H), 4.33 (d, J ) 11.5 Hz, 1H), 4.20 (m, 2H),
4.11 (m, 2H), 4.01 (m, 2H), 3.69 (s, 3H), 3.42 (dd, J ) 5.0, J )
15.0 Hz, 1H), 3.28 (dd, J ) 5.5, J ) 14.5 Hz, 1H), 3.07 (d, J )
4.5 Hz, 2H), 2.75 (d, J ) 6.0 Hz, 2H), 2.11 (s, 3H), 2.06 (s, 3H),
2.01 (s, 3H), 1.95 (s, 3H), 1.47 (s, 9H), 1.34 (d, J ) 7.0 Hz, 3H);
S-[4-(Tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)-2E-butenyl] N-(tert-
butyloxycarbonyl)-γ-L-Glu-(r-OMe)-L-Cys-Gly-OMe (16): 79%
1
yield; [R]23 -40.8 (c 0.2, MeOH); H NMR (500 MHz, CDCl3)
D
δ 5.75 (m, 2H), 5.27 (t, J ) 9.5 Hz, 1H), 5.04 (t, J ) 10.0 Hz,
(14) Sodeoka, M.; Yamada, H.; Shibasaki, M. J. Am. Chem. Soc. 1990, 112,
4906–4911.
(15) When TLC indicated orthoester formation, TMSOTf (0.1 equiv) was
added before the reaction was quenched.
7024 J. Org. Chem. Vol. 73, No. 18, 2008

Synthesis of Neoglycoconjugates
13C NMR (125 MHz, CDCl3) δ 172.1, 171.5, 170.8, 170.5, 170.0,
136.3, 129.8, 129.1, 127.7, 123.6, 122.3, 119.7, 118.6, 111.6, 109.7,
99.9, 80.7, 71.1, 70.7, 69.3, 69.1, 67.4, 61.6, 53.0, 52.7, 49.1, 33.8,
33.2, 29.9, 28.5, 27.6, 21.1, 20.88, 20.85, 20.8, 18.1; ESIHRMS
calcd for C41H57N4O16S [M + H]+ 893.3485, found 893.3480.
General Procedure for the Ligation of Protected Neoglycosyl
Donors with Glutathione. A solution of glutathione (0.05 mmol)
and neoglycosyl donor (0.075 mmol) in Tris buffer (pH 8.0)/
acetonitrile (0.5 mL/0.5 mL) was stirred at room temperature until
completion. Triphenylphosphine (39 mg, 0.15 mmol) dissolved in
tetrahydrofuran (0.5 mL) was added, and the reaction mixture was
stirred at room temperature for 10-24 h. The solution was
evaporated and the residue purified by reversed-phase HPLC using
a gradient of 50% A to 100% A developed over 50 min (A,
0.1%TFA/CH3CN; B, 0.1% TFA/H2O; column: Varian Microsorb
2-(2-Pyridyldisulfanyl)-3-enyl ꢀ-D-cellobioside (25c): white foam,
eluted from silica gel as an approximately 1:1 mixture of diaster-
1
eomers with dichloromethane/methanol (15:1) in 92% yield; H
NMR (500 MHz, CD3OD) δ 8.53 (m, 2 × 1H), 8.13(m, 2 × 2H),
7.50 (m, 2 × 1H), 5.86 (m, 2 × 1H), 5.28 (m, 2 × 1H), 5.18 (m,
2 × 1H), 4.41 (d, J ) 7.5 Hz, 2 × 1H), 4.32 (dd, J ) 8.0, J )
17.0 Hz, 2 × 1H), 4.16 (m, 1H), 4.09 (m, 1H), 3.90 (m, 2 × 4H),
3.80 (m, 2 × 2H), 3.66 (m, 2 × 1H), 3.52 (m, 2 × 2H), 3.36 (m,
2 × 3H), 3.25(m, 2 × 2H); 13C NMR (125 MHz, CD3OD) δ 160.6,
148.8, 138.0, 134.2, 134.1, 121.1, 120.4, 118.5, 118.3, 103.4, 103.2,
79.5, 76.9, 76.7, 75.4, 75.2, 73.7, 73.6, 70.2, 70.1, 61.3, 60.7, 54.2,
54.1; ESIHRMS calcd for C21H31NO11S2Na [M + Na]+ 560.1236,
found 560.1255.
2-(2-Pyridyldisulfanyl)-3-enyl (methyl 5-acetylamino-3,5-dideoxy-
D-glycero-r-D-galacto-non-2-ulopyranosylonate (26): white foam,
eluted from silica gel as an approximately 1:1 mixture of diaster-
C
18 250 × 21.4 mm; flow rate: 8 mL/min; UV detection: 215nm).
1
eomers with dichloromethane/methanol (20:1) in 78% yield; H
S-[4-(Tetra-O-acetyl-ꢀ-D-glucopyranosyloxy)-2E-butenyl] γ-L-
NMR (500 MHz, CD3OD) δ 8.37 (m, 2 × 1H), 7.87 (m, 2 × 1H),
7.81 (m, 2 × 1H), 7.21 (m, 2 × 1H), 5.77 (m, 2 × 1H), 5.20 (m,
2 × 2H), 4.05 (m, 2 × 1H), 3.82 (m, 2 × 2H), 3.80 (s, 3H), 3.78
(s, 3H), 3.64 (m, 2 × 4H), 3.54 (m, 2 × 1H), 3.49 (m, 2 × 1H),
2.66 (m, 2 × 1H), 1.994 (s, 3H), 1.991 (s, 3H), 1.71(m, 2 × 1H);
13C NMR (125 MHz, CD3OD) δ 174.0, 169.47, 169.49, 160.5,
160.4, 148.97, 148.89, 138.0, 133.91, 133.86, 121.2, 121.1, 120.24,
120.21, 118.7, 118.5, 99.05, 99.00, 73.9, 71.2, 71.1, 68.98, 68.9,
67.3, 64.9, 64.87, 63.6, 63.5, 54.2, 53.9, 52.6, 52.3, 40.3, 40.28,
21.5; ESIHRMS calcd for C21H30N2O9S2Na [M + Na]+ 541.1290,
found 541.1305.
General Procedure for the Ligation of Unprotected Neoglyco-
syl Donors with Glutathione. A solution of glutathione (21.7 mg,
0.07 mmol) and neoglycosyl donor (0.11 mmol) in phosphate buffer
(pH 8.0)/acetonitrile (0.5 mL/0.5 mL) was stirred at room temper-
ature until completion (12-24 h). Triphenylphosphine (27.5 mg,
0.11 mmol) dissolved in THF (0.1 mL) was added, and the reaction
mixture was stirred at room temperature for 10-24 h. The solution
was evaporated and the mixture purified by reverse phase HPLC
using a gradient of 100% B to 50% B developed over 50 min (A,
0.1%TFA/CH3CN; B, 0.1% TFA/H2O; column: Varian Microsorb
Glu-L-Cys-Gly (23): 75% yield; [R]24 -13.3 (c 0.6, MeOH); H
1
D
NMR (500 MHz, D2O) δ 5.60 (m, 2H), 5.24 (t, J ) 9.5 Hz, 1H),
4.98 (t, J ) 9.5 Hz, 1H), 4.84 (t, J ) 8.5 Hz, 1H), 4.76 (d, J ) 8.5
Hz, 1H), 4.42 (m, 1H), 4.23 (m, 2H), 4.10 (m, 2H), 3.91 (m, 3H),
3.85 (t, J ) 6.5 Hz, 1H), 3.10 (d, J ) 6.0 Hz, 2H), 2.87 (dd, J )
5.4, J ) 14.0 Hz, 1H), 2.68 (m, 1H), 2.44 (m, 2H), 2.08 (m, 2H),
1.99 (s, 3H), 1.98 (s, 3H), 1.95 (s, 3H), 1.91 (s, 3H); 13C NMR
(125 MHz, D2O) δ 174.3, 173.7, 173.1, 172.85, 172.77, 172.66,
171.9, 130.6, 128.2, 98.8, 73.1, 71.5, 71.1, 69.5, 68.3, 61.8, 52.8,
52.5, 41.0, 32.6, 31.4, 30.9, 25.5, 20.14, 20.11, 20.03, 19.99;
ESIHRMS calcd for C28H41N3O16SNa [M + Na]+ 730.2105, found
730.2102.
S-[4-(Methyl 4,7,8,9-tetra-O-acetyl-5-acetylamino-3,5-dideoxy-
D-glycero-r-D-galacto-non-2-ulopyranosylonate)-2E-butenyl] γ-L-
Glu-L-Cys-Gly (24): 71% yield; [R]24 -9.2 (c 0.6, MeOH/H2O,
D
1
1:1); H NMR (500 MHz, D2O) δ 5.64 (m, 2H), 5.29 (m, 2H),
4.80 (m, 2H), 4.45 (m, 1H), 4.26 (m, 1H), 4.15 (m, 3H), 3.99 (t, J
) 6.5 Hz, 1H), 3.95 (m, 1H), 3.92 (s, 2H), 3.83 (t, J ) 10.5 Hz,
1H), 3.77 (s, 3H), 3.13 (d, J ) 6.5 Hz, 2H), 2.89 (dd, J ) 5.5, J
) 14.0 Hz, 2H), 2.71 (m, 1H), 2.63 (dd, J ) 5.0, J ) 13.0 Hz,
1H), 2.50 (m, 2H), 2.16 (m, 2H), 2.11 (s, 3H), 2.06 (s, 3H), 1.99
(s, 3H), 1.94 (s, 3H), 1.82 (s, 3H); 13C NMR (125 MHz, D2O) δ
175.1, 174.5, 173.9, 173.7, 173.6, 173.2, 173.1, 172.6, 169.0, 132.7,
126.5, 98.8, 71.8, 69.4, 68.5, 67.5, 62.4, 57.4, 55.8, 53.9, 53.6, 49.0,
41.6, 37.2, 26.1, 25.5, 22.0, 20.7, 20.4, 20.3; ESIHRMS calcd for
C34H50N4O19SNa [M + Na]+ 873.2688, found 873.2699.
General Procedure for Preparation of Deprotected Neoglyco-
syl Donors from Acetylated Allylic Thiocarbonates. The peracetyl
glycosyl thiolcarbonate (0.2 mmol) was dissolved in MeOH (1 mL)
at 0 °C with stirring and 1 M KOH in MeOH (1.2 mmol-2.1 mmol,
1.5 equiv per acetate group) was added dropwise. After 10-15
min, the pH of the reaction mixture was adjusted to 7 by careful
addition of Amberlyst-15. The reaction mixture was then filtered,
and the filtrate was added dropwise over 15 min to a well-stirred
solution of 2,2′-dipyridyl disulfide (68 mg, 0.3 mmol) in MeOH (1
mL) at room temperature and the resulting solution stirred until
completion (TLC, ∼3 h). The solvent was removed in vacuo and
the residue taken up in H2O and washed with ether several times.
Evaporation of the aqueous phase followed by chromatographic
purification gave the products.
2-(2-Pyridyldisulfanyl)-3-enyl ꢀ-D-galactopyranoside (25b): white
foam, eluted from silica gel as an approximately 1:1 mixture of
diastereomers with dichloromethane/methanol (20:1) in 92% yield; 1H
NMR (500 MHz, CD3OD) δ 8.36 (m, 2 × 1H), 7.94 (m, 2 × 1H),
7.81(m, 2 × 1H), 7.20 (m, 2 × 1H), 5.86 (m, 1H), 5.81 (m, 1H), 5.23
(m, 2 × 1H), 5.14 (d, J ) 10.5 Hz, 2 × 1H), 4.24 (m, 2 × 1H), 4.13
(m, 2 × 1H), 3.80 (m, 2 × 3H), 3.72 (m, 2 × 2H), 3.55 (2 × 1H, m),
3.47(m, 2 × 2H); 13C NMR (125 MHz, CD3OD) δ 160.6, 148.8, 138.0,
134.24, 134.20, 121.0, 120.4, 118.4, 118.2, 104.04, 103.96, 75.6, 73.8,
71.3, 70.1, 69.1, 61.3, 61.2, 54.3; ESIHRMS calcd for C15H21NO6S2Na
[M + Na]+ 398.0708, found 398.0706.
C
18 250 × 21.4 mm; flow rate: 8 mL/min; UV detection: 215nm).
S-[4-(ꢀ-D-Galactopyranosyloxy)-2E-butenyl] γ-L-Glu-L-Cys-Gly
(27): 90% yield; [R]23D -18.9 (c 1.0, MeOH); 1H NMR (400 MHz,
D2O) δ 5.77 (m, 2H), 4.52 (m, 1H), 4.38 (d, J ) 8.4 Hz, 1H), 4.35
(dd, J ) 3.2, J ) 12.0 Hz, 1H), 4.20 (m, 1H), 4.08 (t, J ) 6.4 Hz,
1H), 3.99 (s, 2H), 3.88 (d, J ) 3.2 Hz, 1H), 3.73 (m, 2H), 3.61 (m,
2H), 3.48 (m, 1H), 3.20 (d, J ) 5.6 Hz, 2H), 2.96 (m, 1H), 2.79
(m, 1H), 2.56 (m, 2H), 2.22 (m, 2H); 13C NMR (100 MHz, D2O)
δ 174.5, 173.13, 173.07, 171.7, 130.7, 130.0, 102.0, 75.4, 73.1,
71.0, 69.7, 68.91, 61.2, 53.2, 52.4, 41.4, 33.0, 31.8, 31.1, 25.7;
ESIHRMS calcd for C20H31N3O12S [M - H]- 538.1707, found
538.1689.
S-[4-(ꢀ-D-Cellobiosyloxy)-2E-butenyl] γ-L-Glu-L-Cys-Gly (28):
92% yield; [R]23 -0.4 (c 1.7, MeOH); 1H NMR (400 MHz,
D
CD3OD) δ 5.76 (m, 2H), 4.57 (m, 1H), 4.40 (d, J ) 8.0 Hz, 1H),
4.35 (m, 2H), 4.16 (m, 1H), 4.05 (m, 1H), 3.94 (s, 2H), 3.86 (m,
2H), 3.66 (m, 1H), 3.54 (m, 2H), 3.39 (m, 2H), 3.31 (m, 3H), 3.25
(m, 2H), 3.19 (d, J ) 5.6 Hz, 2H), 2.95 (m, 1H), 2.71 (m, 1H),
2.57 (m, 2H), 2.20 (m, 2H); 13C NMR (100 MHz, CD3OD) δ 173.2,
171.9, 171.5, 170.3, 129.6, 129.3, 103.5, 101.9, 79.6, 76.9, 76.7,
75.3, 75.2, 73.7, 73.6, 70.2, 68.9, 61.2, 60.6, 53.0, 52.3, 48.7, 40.6,
33.1, 32.2, 31.1, 25.9; ESIHRMS calcd for C26H42N3O17S [M -
H]- 700.2235, found 700.2229.
S-[4-(Methyl (5-acetamido-3,5-dideoxy-D-glycero-r-D-galacto-
non-2-ulopyranoside)onate)-2E-butenyl] γ-L-Glu-L-Cys-Gly (29):
94% yield; [R]23D -13.8 (c 1.4, MeOH); 1H NMR (400 MHz, D2O)
δ 5.77 (m, 2H), 4.51 (m, 1H), 4.27 (m, 1H), 4.06 (m, 2H), 3.99 (s,
2H), 3.83 (m, 7H), 3.71 (m, 1H), 3.62 (m, 1H), 3.52 (d, J ) 9.2
Hz, 1H), 3.18 (d, J ) 5.6 Hz, 1H), 2.94 (m, 1H), 2.77 (m, 1H),
2.67 (m, 1H), 2.56 (m, 2H), 2.22 (m, 2H), 2.00 (s, 3H), 1.78 (t, J
) 12.0 Hz, 1H); 13C NMR (100 MHz, D2O) δ 175.3, 174.5, 173.1,
J. Org. Chem. Vol. 73, No. 18, 2008 7025

Crich and Yang
173.0, 171.7, 170.3, 130.5, 128.7, 99.1, 73.2, 70.9, 68.5, 67.4, 65.0,
63.4, 53.7, 53.2, 52.4, 52.0, 41.3, 39.6, 33.0, 31.8, 31.1, 25.7, 22.3;
ESIHRMS calcd for C26H42N4O15SNa [M + Na]+ 705.2265, found
705.2265.
0.59 mmol) in DMF (1.7 mL) at 0 °C. The reaction mixture
was stirred at room temperature overnight and then concentrated
and the residue taken up in toluene and concentrated again to
give yellow oil, which was lyophilized to remove N-methylpyr-
rolidone and then subjected to flash chromatography to afford
the pure N-glycosylamide.
N-(ꢀ-D-Glucopyranosyl) 3-[(2-pyridinyl)disulfanyl]-4-pentena-
mide (36a): white foam, eluted from silica gel with dichlo-
romethane/methanol (3:1) as an approximately 1:1 mixture of
diastereomers in 46% yield: 1H NMR (400 MHz, D2O) δ 8.34 (d,
J ) 4.8 Hz, 2 × 1H), 7.79 (m, 2 × 2H), 7.25 (m, 2 × 1H), 5.73
(m, 2 × 1H), 5.13 (d, J ) 17.2 Hz, 2 × 1H), 5.04 (d, J ) 9.6 Hz,
2 × 1H), 3.87 (m, 2 × 2H), 3.69 (m, 2 × 1H), 3.50 (m, 2 × 2H),
3.35 (m, 2 × 2H), 2.77 (m, 2 × 2H); 13C NMR (100 MHz, D2O)
δ 174.4, 159.0, 149.1, 138.8, 135.1, 122.2, 121.8, 118.6, 118.5,
79.6, 77.9, 76.8, 72.0, 69.5, 60.8, 49.93, 49.86, 39.5, 39.4;
ESIHRMS calcd for C16H22N2O6S2Na [M + Na]+ 425.0817, found
428.0824.
N-(2-Acetamido-2-deoxy-ꢀ-D-glucopyranosyl) 3-[(2-pyridinyl)-
disulfanyl]-4-pentenamide (36b): white foam, eluted from silica gel
with dichloromethane/methanol (3:1) as an approximately 1:1
mixture of diastereomers in 43% yield: 1H NMR (400 MHz, D2O)
δ 8.37 (m, 2 × 1H), 7.83 (m, 2 × 2H), 7.28 (m, 2 × 1H), 5.72 (m,
2 × 1H), 5.07 (m, 2 × 3H), 3.88 (m, 2 × 2H), 3.77 (m, 2 × 2H),
3.60 (m, 2 × 1H), 3.35 (m, 2 × 2H), 2.74 (m, 2 × 2H), 1.98 (s,
3H), 1.97 (s, 3H); 13C NMR (100 MHz, CD3OD) δ 173.1, 173.0,
171.5, 160.24, 160.15, 149.0, 148.9, 137.91, 137.87, 135.6, 135.5,
121.2, 121.1, 120.20, 120.15, 117.5, 117.3, 79.1, 79.0, 78.62, 78.59,
75.20, 75.16, 70.61, 70.58, 61.5, 54.9, 50.2, 50.0, 39.7, 39.6, 21.9,
21.8; ESIHRMS calcd for C18H25N3O6S2Na [M + Na]+ 466.1082,
found 466.1100.
General Procedure for Ligation of N-Glycosyl 3-[(2-Pyridinyl)-
disulfanyl]-4-pentenamides with Peptides. A solution of cysteine
containing peptide (0.05 mmol) and the N-glycosylamide (0.075
mmol) in phosphate buffer (pH 8.0)/acetonitrile (0.5 mL/0.5 mL)
was stirred at room temperature until completion (12-24 h).
Triphenylphosphine (26 mg, 0.1 mmol) dissolved in THF (0.1
mL) was then added, and the reaction mixture was stirred at
room temperature for 10-24 h. The solution was evaporated
and the residue purified by reverse phase HPLC using a gradient
of 100% B to 50% B developed over 70 min (A, 0.1% TFA/
CH3CN; B, 0.1% TFA/H2O; column: Varian Microsorb C18 250
× 21.4 mm; flow rate: 8 mL/min; UV detection: 215nm).
tert-Butyl 3-Acetylthio-4-pentenoate (32). Diisopropyl azodicar-
boxylate (5.1 mL, 26 mmol) was added to a stirred solution of
triphenylphosphine (6.85 g, 26 mmol) in tetrahydrofuran (46 mL)
at 0 °C over 0.5 h, resulting in the formation of a white precipitate.
A solution of alcohol 3116 (3.0 g, 17.4 mmol) and thiolacetic acid
(1.87 mL, 26 mmol) in tetrahydrofuran (20 mL) was then added
dropwise, and the mixture was stirred for 1 h at 0 °C and at room
temperature for 13 h resulting in a clear yellow solution. The
reaction mixture was diluted with ethyl acetate and washed with
water. The organic layer was dried, filtered, evaporated, and purified
by chromatography (eluting with hexane/ethyl acetate, 10:1) to give
1
32 (3.06 g, 76%) as yellow oil: H NMR (500 MHz, CDCl3) δ
5.86 (m, 2 × 1H), 5.26 (d, J ) 17.0 Hz, 2 × 1H), 5.10 (d, J )
10.5 Hz, 2 × 1H), 4.42 (q, J ) 7.5 Hz, 2 × 1H), 2.63 (m, 2 ×
2H), 2.31 (s, 2 × 3H), 1.43(s, 2 × 9H); 13C NMR (125 MHz,
CDCl3) δ 195.4, 169.8, 136.6, 116.7, 81.4, 42.5, 40.2, 30.8, 28.3;
ESIHRMS calcd for C11H18O3SNa [M + Na]+ 253.0874, found
253.0895.
tert-Butyl 3-[(2-Pyridinyl)disulfanyl]-4-pentenoate (33). Lithium
hydroxide monohydrate (30 mg, 0.71 mmol) was added in one
portion to a stirred solution of thiolacetate 32 (163 mg, 0.71 mmol)
in methanol (3.5 mL) at 0 °C. After 0.5 h, the pH of the solution
was adjusted to 7 with 3 M HCl, and the resulting solution was
added dropwise to a stirred solution of 2,2′-dipyridyl disulfide (239
mg, 1.06 mmol) in dichloromethane (3 mL) over 15 min. After the
solution was stirred for 3 h, the solvent was removed. The residue
was dissolved in ethyl acetate and washed with water. The organic
layer was dried, filtered, evaporated, and purified by chromatog-
raphy on silica gel17 (eluting with hexane/ethyl acetate, 10:1) to
1
afford 33 (144 mg, 68%) as a yellow oil: H NMR (500 MHz,
CDCl3) δ 8.44 (dd, J ) 0.5, J ) 4.5 Hz, 2 × 1H), 7.72 (d, J ) 7.5
Hz, 2 × 1H), 7.63 (dt, J ) 2.0, J ) 7.5 Hz, 2 × 1H), 7.08 (dt, J
) 1.0, J ) 7.5 Hz, 2 × 1H), 5.76 (m, 2 × 1H), 5.18 (d, J ) 17.0
Hz, 2 × 1H), 5.10 (d, J ) 10.0 Hz, 2 × 1H), 3.86 (q, J ) 8.5 Hz,
2 × 1H), 2.77 (dd, J ) 6.5, J ) 15.5 Hz, 2 × 1H), 2.59 (dd, J )
8.5, J ) 16.0 Hz, 2 × 1H), 1.43(s, 2 × 9H); 13C NMR (125 MHz,
CDCl3) δ 170.0, 160.6, 149.6, 137.1, 135.6, 120.9, 120.0, 118.3,
81.5, 50.0, 39.8, 28.3; ESIHRMS calcd for C14H19NO2S2Na [M +
Na]+ 320.0755, found 320.0766.
3-[(2-Pyridinyl)disulfanyl]-4-pentenoic Acid (34). Trifluoroacetic
acid (1.36 mL, 17.5 mmol) was added dropwise over 20 min into
a stirred solution of ester 33 (208 mg, 0.7 mmol) in dichloromethane
(1.4 mL) at 0 °C. The reaction mixture was stirred for 4-5 h at
room temperature and then concentrated, taken up in toluene, and
concentrated again to afford 34 (169 mg, 100%) as yellow syrup:
1H NMR (400 MHz, CDCl3) δ 12.34 (br. s, 2 × 1H), 8.59 (d, J )
4.8 Hz, 2 × 1H), 7.87 (m, 2 × 2H), 7.35 (t, J ) 6.0 Hz, 2 × 1H),
5.80 (m, 2 × 1H), 5.20 (m, 2 × 2H), 3.93 (q, J ) 7.2 Hz, 2 ×
1H), 2.82(m, 2 × 2H); 13C NMR (100 MHz, CDCl3) δ 159.0, 147.1,
140.3, 134.7, 122.7, 122.4, 119.2, 50.0, 38.4, 29.9; ESIHRMS calcd
for C10H11NO2S2Na [M + Na]+ 264.0129, found 264.0147.
General Procedure for Formation of N-Glycosyl 3-[(2-Pyridi-
nyl)disulfanyl]-4-pentenamides.18 A solution of ꢀ-D-glucopyra-
nosyl azide or 2-acetamido-2-deoxy-ꢀ-D-glucopyranosyl azide
(1.18 mmol) in N-methylpyrrolidone (4 mL) was stirred with
10% Pd/C under H2 (1 atm) at room temperature until TLC
indicated completion (∼5 h). After filtration, the reaction mixture
was added dropwise over 0.5 h to a stirred, premixed solution
of O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium
hexafluorophosphate (HATU) (231 mg, 0.59 mmol) and diiso-
propylethylamine (202 µL, 1.18 mmol) and acid 34 (142 mg,
S-[N-(ꢀ-D-Glucopyranosyl)-5-carboxamido-2E-butenyl] γ-L-Glu-
L-Cys-Gly (37): 70% yield; [R]23D -18.5 (c 0.6, MeOH/H2O 1:1);
1H NMR (400 MHz, D2O) δ 5.66 (m, 2H), 4.94 (d, J ) 8.8 Hz,
1H), 4.53 (m, 1H), 4.04 (t, J ) 6.4 Hz, 1H), 4.00 (s, 2H), 3.86 (m,
1H), 3.70 (dd, J ) 4.8, J ) 12.0 Hz, 1H), 3.51 (m, 1H), 3.59 (t, J
) 8.4 Hz, 1H), 3.38 (m, 2H), 3.27 (m, 2H), 3.20 (d, J ) 6.4 Hz,
2H), 3.11 (d, J ) 4.8 Hz, 1H), 2.97 (dd, J ) 5.4, J ) 14.2 Hz,
1H), 2.80 (m, 1H), 2.57 (m, 2H), 2.22 (m, 2H); 13C NMR (100
MHz, D2O) δ 176.1, 174.6, 173.2, 173.1, 172.2, 130.6, 126.1, 79.6,
77.9, 76.8, 72.0, 69.5, 60.8, 53.2, 52.8, 47.8, 41.4, 39.2, 33.2, 31.6,
31.2, 25.9; ESIHRMS calcd for C21H35N4O12S [M + H]+ 567.1972,
found 567.1967.
S-[N-(2-Acetamido-2-deoxy-ꢀ-D-glucopyranosyl)-5-carboxamido-
2E-butenyl] γ-L-Glu-L-Cys-Gly (38): 85% yield; [R]23D -3.4 (c 0.7,
MeOH/H2O 1:1); 1H NMR (400 MHz, D2O) δ 5.52 (m, 2H), 5.03
(d, J ) 9.6 Hz, 1H), 4.52 (m, 1H), 4.04 (t, J ) 6.4 Hz, 1H), 4.00
(s, 2H), 3.86 (dd, J ) 1.6, J ) 12.0 Hz, 1H), 3.80 (t, J ) 10.0 Hz,
1H), 3.73 (dd, J ) 4.8, J ) 12.0 Hz, 1H), 3.59 (t, J ) 8.4 Hz, 1H),
3.48 (m, 2H), 3.19 (d, J ) 5.6 Hz, 2H), 3.03 (d, J ) 4.8 Hz, 2H),
3.00 (dd, J ) 5.6, J ) 14.0 Hz, 1H), 2.78 (dd, J ) 8.8, J ) 14.4
Hz, 1H), 2.57 (m, 2H), 2.22 (m, 2H), 1.98 (s, 3H); 13C NMR (100
MHz, D2O) δ 175.5, 175.0, 174.6, 173.2, 173.1, 130.7, 126.0, 78.8,
77.9, 74.4, 69.8, 60.8, 54.6, 53.2, 52.7, 41.4, 39.3, 33.3, 31.8, 31.2,
25.8, 22.3; ESIHRMS calcd for C23H37N5O12SNa [M + Na]+
630.2057, found 630.2072.
(16) Zibuck, R.; Streiber, J. M. J. Org. Chem. 1989, 54, 4717–4719.
(17) This compound showed a tendency to undergo allylic rearrangement
during silica gel chromatography when moisture was not fully excluded.1c
(18) Wen, S.; Guo, Z. Org. Lett. 2001, 3, 3773–3776.
7026 J. Org. Chem. Vol. 73, No. 18, 2008

Synthesis of Neoglycoconjugates
S-[N-(2-Acetamido-2-deoxy-ꢀ-D-glucopyranosyl)-5-carboxamido-
22.2, 19.0, 17.9, 17.0; ESIHRMS calcd for C27H47N6O12S [M +
2E-butenyl] L-Val-L-Thr-L-Cys-Gly (40): 70% yield; [R]23 -8.9
H]+ 679.2973, found 679.2997.
D
1
(c 0.2, MeOH/H2O 1:1); H NMR (500 MHz, D2O) δ 5.50 (m,
Acknowledgment. We thank the NIH (GM62160) for partial
support of this work and Dr. Franck Brebion for help and advice
in the initial stages of the project.
2H), 4.92 (d, J ) 10.0 Hz, 1H), 4.45 (m, 1H), 4.32 (d, J ) 6.5 Hz,
1H), 4.03 (m, 1H), 3.88 (s, 2H), 3.80 (d, J ) 5.5 Hz, 1H), 3.75 (m,
1H), 3.69 (t, J ) 10.0 Hz, 1H), 3.62 (dd, J ) 4.5, J ) 12.0 Hz,
1H), 3.48 (t, J ) 9.2 Hz, 1H), 3.37 (m, 2H), 3.07 (d, J ) 6.0 Hz,
2H), 2.92 (d, J ) 4.5 Hz, 2H), 2.86 (d, J ) 5.0 Hz, J ) 14.0 Hz,
1H), 2.69 (m, 1H), 2.12 (m, 1H), 1.87 (s, 3H), 1.10 (d, J ) 6.0 Hz,
3H), 0.90 (t, J ) 7.0 Hz, 6H); 13C NMR (125 MHz, D2O) δ 175.3,
174.9, 173.1, 172.3, 171.2, 169.7, 130.6, 125.8, 78.7, 77.8, 74.3,
69.7, 67.3, 60.7, 59.3, 58.6, 54.5, 52.9, 50.6, 41.4, 39.2, 30.5, 24.0,
1
Supporting Information Available: Copies of H and 13C
NMR data for all new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
JO8015314
J. Org. Chem. Vol. 73, No. 18, 2008 7027