Design and synthesis of conformationally constrained glycosylated amino acids

Article abstract of DOI:10.1021/jo001512z

To probe the conformational requirements of O-linked glycoproteins for binding to various enzymes and receptors, two conformationally constrained glycosylated amino acids, 2 and 3, were designed. The analogues were found to represent two potential low energy conformations of the parent conjugate, 1, by molecular modeling. A convergent synthesis of both 2 and 3 from D-galactose and L-methionine is presented.

Full text of DOI:10.1021/jo001512z

2318
J . Org. Chem. 2001, 66, 2318-2326
Design a n d Syn th esis of Con for m a tion a lly Con str a in ed
Glycosyla ted Am in o Acid s
J ennifer L. Koviach, Mark D. Chappell, and Randall L. Halcomb*
Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215
halcomb@colorado.edu
Received October 23, 2000
To probe the conformational requirements of O-linked glycoproteins for binding to various enzymes
and receptors, two conformationally constrained glycosylated amino acids, 2 and 3, were designed.
The analogues were found to represent two potential low energy conformations of the parent
conjugate, 1, by molecular modeling. A convergent synthesis of both 2 and 3 from D-galactose and
L-methionine is presented.
Peptides that contain conformational constraints have
allowed access to a wealth of data concerning the
conformations of ligands that are bound by biological
receptors and have been valuable in the development of
pharmaceutical agents.1 Additionally, conformationally
constrained peptides are indispensable tools in elucidat-
ing principles that govern polypeptide secondary struc-
ture.1 While the ground-state solution structures of small
glycopeptide fragments are well studied,2 little is known
about the conformations that are recognized by enzymes
and receptors. To probe this issue, several glycoconju-
gates that contain conformational constraints have been
synthesized and evaluated, but in general, these concepts
are not well developed.3
F igu r e 1.
One prevalent class of glycoproteins consists of the
O-linked group4 and is characterized by the R-N-acetyl-
galactosaminyl (GalNAc) serine (or threonine) linkage as
represented by the tumor-associated sialyl T antigen
(Figure 1). This class is often found on the surfaces of
cells in the circulatory and immune systems, among other
locations. The sialyl T antigen is present on the surface
of several metastatic tumor cell types and is a current
target for cancer immunotherapy.5 This report describes
a strategy for constraining torsional angles about the
bonds linking the peptide to the carbohydrate compo-
nents within this class. The constrained glycopeptides
have the potential to be useful tools in understanding
the conformational requirements for binding to various
receptors and enzymes.
F igu r e 2.
In general, the conformation of the C1-O1 bond of the
carbohydrate moiety of motifs such as 1 (Figure 2) is
somewhat rigid and can be predicted by the anomeric and
exo-anomeric effects.6 The remaining bonds linking car-
bohydrate to peptide, specifically ø2, in the serine/
threonine side chain are more flexible. The targets chosen
for this study are the glycosylated amino acids 2 and 3,
in which rotation about the torsional angle ø2 is restricted
by incorporation of the side chain into a small ring.7
Incorporation of 2 and 3 into peptides and evaluation of
the binding of the resulting constructs to receptors and
enzymes whose parent ligands are the native glycopep-
tides will ideally provide valuable information about the
conformations of the ligand that are selected for binding.
To determine if the proposed conformationally con-
strained analogues actually represent reasonable con-
formations of the native GalNAc-Ser, a molecular mod-
eling analysis was performed. To avoid problems related
to charge, the amine was capped with an acetyl group,
and the carboxylate was cloaked as a methyl ester.
(1) (a) Hruby, V. J .; Bonner, G. G. In Methods in Molecular Biology;
Pennigton, M. W., Dunn, B. M., Eds.; Humana Press: Totowa, NJ ,
1994; Vol. 35, pp 201-240. (b) Obrecht, D.; Altorfer, M.; Robinson, J .
A. Adv. Med. Chem. 1999, 4, 1-68. (c) Goodman, M.; Shao, H. Pure
Appl. Chem. 1996, 68, 1303-1308.
(2) (a) Kirnarsky, L.; Prakash, O.; Vogen, S. M.; Nomoto, M.;
Hollingsworth, M. A. Sherman, S. Biochemistry 2000, 39, 12076-
12082. (b) Wu, W.; Pasternack, L.; Huang, D.-H.; Koeller, K. M.; Lin,
C.-C.; Seitz, O.; Wong, C.-H. J . Am. Chem. Soc. 1999, 121, 2409-2417.
(c) O’Connor, S. E.; Imperiali, B. Chem. Biol. 1998, 5, 427-437. (d)
Liang, R.; Andreotti, H.; Kahne, D. J . Am. Chem. Soc. 1995, 117,
10395-10396. (e) Meyer, B. Top. Curr. Chem. 1990, 154, 141-208.
(3) (a) Davis, B. G. J . Chem. Soc., Perkin Trans. 1 2000, 2137-2160.
(b) Navarre, N.; vanOijen, A. H.; Boons, G. J . Tetrahedron Lett. 1997,
38, 2023-2026. (c) Geyer, A.; Muller, M.; Schmidt, R. R. J . Am. Chem.
Soc. 1999, 121, 6312-6313. (d) Alibes, R.; Bundle, D. R. J . Org. Chem.
1998, 63, 6288-6301.
(6) Deslongchamps, P. Stereoelectronic Effects in Organic Chemistry;
Pergamon: New York, 1983.
(7) For more examples of constraining ø2, see: Gibson, S. E.; Guillo,
N.; Tozer, M. J . Tetrahedron 1999, 55, 585-615.
(4) Dwek, R. A. Chem. Rev. 1996, 96, 683-720.
(5) Danishefsky, S. J .; Allen, J . R. Angew. Chem., Int. Ed. Engl.
2000, 39, 837-863.
10.1021/jo001512z CCC: $20.00 © 2001 American Chemical Society
Published on Web 03/09/2001

Synthesis of Glycosylated Amino Acids
J . Org. Chem., Vol. 66, No. 7, 2001 2319
F igu r e 3.
Sch em e 1
Molecular modeling of 4, 5, and 6 (Figure 3) utilizing the
AMBER force field, which included the carbohydrate
potentials developed by Homans,8 afforded low energy
conformations, and ø2 was measured for each compound.
As expected, it was found that the lowest energy confor-
mation of native GalNAc-Ser (4) contains an anti rela-
tionship between the anomeric carbon of the sugar and
the R-carbon of the peptide backbone (ø2 ) 174°). Al-
though this protocol resulted in a single low energy
conformation, structures with a gauche relationship (ø2
≈ (60°) should also be considered as potential bound
conformations. In actuality, compounds 5 and 6 contain
torsional angles ø2 187° and -89°, respectively. These
results suggest that the analogue 2 is a good structural
replacement for the anti conformation, while 3 ap-
proximates one of the two possible gauche conformations.
Since these conformationally constrained glycopeptides
represent potential low energy conformations of the
parent glycopeptide, a synthesis of each one was under-
taken.
The synthesis plan for 2 and 3, which contain suitable
protecting groups for peptide synthesis, is shown in
Scheme 1. Since 2 and 3 differ by a single stereocenter,
it was anticipated that both compounds could be con-
structed through independent but similar sequences. A
convergent synthesis was devised, in which an L-me-
thionine-derived alkyne would be joined with a D-galactose-
derived lactone. Nonstereoselective introduction of a
secondary alcohol stereocenter in an early intermediate
derived from L-methionine would be followed by separa-
tion of the diastereomers to afford the acetylides 7a and
7b as key intermediates. The sugar component of 2 and
3 could be derived from the suitably protected 2-deoxy-
2-azidogalactonolactone 8, which in turn could arise from
D-galactose. The C2-azide was chosen as a masked
version of the acetamide due the stability of azides to
carbon nucleophiles such as 7a and 7b. The key C-
glycosylation step could be accomplished by addition of
the acetylide 7a or 7b to the lactone 8 to afford 9a and
9b, respectively. Reduction of the alkyne and subsequent
acid-induced spiroketalization would give 10a and 10b
after protecting group adjustments. The spiroketalization
was predicted to afford the product in which each ketal
oxygen is axial to the opposing ring, according to stereo-
electronic principles.9
The synthesis of 10a and 10b began with the olefin
11, which was prepared in five steps from L-methionine.10
Attempted epoxidation of the olefin under a variety of
standard conditions (m-CPBA, m-CPBA + base, tert-
butylhydroperoxide, Oxone-acetone, DCC-H2O2) was
problematic, but fortunately, treatment of 11 with excess
anhydrous dimethyldioxirane11 afforded a 79:21 mixture
of diastereomers 12a and 12b in 84% combined yield
(8) (a) Homans, S. W. Biochemistry 1990, 29, 9110-9118. (b) Weiner,
S. J .; Kollman, P. A.; Case, D. A.; Singh, U. C.; Ghio, C.; Alagona, G.;
Profeta, S.; Weiner, P. J . Am. Chem. Soc. 1984, 106, 765-784. (c)
Weiner, S. J .; Kollman, P. A.; Nguyen, D. T.; Case, D. A. J . Comput.
Chem. 1986, 7, 230-252.
(9) Perron, R.; Albizati, K. F. Chem. Rev. 1989, 89, 1617-1661.
(10) Kumar, J . S.; Datta, A. Tetrahedron Lett. 1997, 38, 6779-6780.
(11) Curci, R.; Dinoi, A.; Rubino, M. F. Pure Appl. Chem. 1995, 67,
811-822.

2320 J . Org. Chem., Vol. 66, No. 7, 2001
Koviach et al.
Sch em e 2a
Sch em e 4a
a
Reagents and conditions: dimethyldioxirane, CH2Cl2, rt, 12
h.
Sch em e 3a
a
Reagents and conditions: (a) TBSOTf, pyr, 0 °C to rt, 24 h;
(c) PPh3‚HBr, THF, H2O, rt, 6 h; (d) PCC, NaOAc, CH2Cl2, rt, 2 h;
(e) KHMDS, THF, -78 °C, 45 min; Trisyl-N3, -96 °C, 5 min;
AcOH, -96 °C to rt, 1 h.
tively silylated with TBDPSCl in pyridine according to
a published procedure to give 15,13 and the remaining
C3 and C4 hydroxyl groups were protected as tert-
butyldimethylsilyl (TBS) ethers to afford 16. When the
glycal 16 was exposed to the standard azidonitration
conditions developed by Lemieux (ceric ammonium ni-
trate, sodium azide) to introduce the C2 azide,14 the
intermediate glycosyl nitrate was found to decompose
rapidly. A more successful alternative was developed in
which glycal 16 was hydrated using a modification of the
procedure developed by Falck and co-workers,15 and the
resulting hemiacetal was oxidized with PCC to give the
lactone 17 in 74% for two steps. The 2-azido functional
group was installed by sequential enolization of 17 with
KHMDS, trapping with 2,4,6-triisopropylphenylsulfonyl
azide (Trisyl-N3), and quenching with acetic acid to afford
the azidolactone 18 in 56% yield.16 It is worth noting that
although similar 2-azidolactones are reported to be
unstable,16 compound 18 could be chromatographed on
neutral silica gel and stored at 0 °C for several months
with no noticeable decomposition.
a
Reagents and conditions: (a) trimethylsilylacetylene, n-BuLi,
THF, 0 °C, 20 min; 12a or 12b, BF3‚Et2O, -78 °C, 1 h; (b) TBAF,
AcOH, THF, rt, 30 min; (c) MSTFA, CH3CN, rt, 12 h.
(Scheme 2). The structure of the major diastereomer was
assigned as 12a by comparison of its spectral data with
that previously reported for the same compound,12 and
the structure of the minor diastereomer 12b was con-
firmed by X-ray crystallographic analysis (see the Sup-
porting Information).
Since the newly formed stereocenter corresponds to C-3
of 10a and 10b, both 12a and 12b could be productively
utilized. The diastereomeric epoxides were separated
chromatographically, and carried through the sequence
separately (Scheme 3). Opening of the epoxides with the
lithium trimethylsilylacetylide afforded secondary alco-
hols 13a (90%) and 13b (94%). The acetylenic silyl group
was removed with fluoride, and the secondary alcohol
was protected as a silyl ether. While more standard
alcohol silylation conditions (TMSCl, amine base) failed,
and silylation with TMSOTf was accompanied by migra-
tion of the acetonide, simply stirring the secondary
alcohols with N-methyl-N-(trimethylsilyl)trifluoroacet-
amide (MSTFA), either neat or in CH3CN, afforded the
alkynes 14a and 14b in excellent yields (100% and 91%,
respectively).
The lactone 18 was prepared as described in Scheme
4. A key aspect of the synthesis was the choice of
protecting groups for the sugar hydroxyls. The protecting
groups were required to be stable to both acetylide
addition as well as the acidic conditions necessary for
spiroketalization. Therefore, silyl groups were chosen,
with a more acid stable tert-butyldiphenylsilyl (TBDPS)
group on the primary C6 alcohol. D-Galactal was selec-
At this stage, it was necessary to form the C-glycoside
by addition of the acetylide anions derived from 14a and
14b to the lactone 18. Deprotonation of alkynes 14a and
14b with n-BuLi and addition to the lactone 18 in the
presence of TMEDA at -78 °C gave the hemiketal
products 19a and 19b in 77% and 62% respectively
(Scheme 5).17 If the reaction was carried out in the
absence of TMEDA, the trimethylsilyl group in 14 was
cleaved, and no addition of the acetylide to the lactone
occurred. The alkyne in 19a or 19b could be exhaustively
hydrogenated with Pd/C in methanol to provide the
corresponding alkane, but there were a few problematic
issues associated with the latter intermediate. Under
these hydrogenation conditions, the trimethylsilyl group
was also removed. But when the resulting secondary
alcohol was treated with a variety of acids to induce
spiroketalization, under no conditions was the desired
spiroketal observed.
(13) Kozikowksi, A. P.; Lee, J . J . Org. Chem. 1990, 55, 863-870.
(14) Lemieux, R. U.; Ratcliffe, R. M. Can. J . Chem. 1979, 57, 1244-
1251.
(15) Bolitt, V.; Mioskowski, C.; Lee, S.-G.; Falck, J . R. J . Org. Chem.
1990, 55, 5812-5813.
(16) Dupradeau, F. Y.; Hakomori, S.; Toyokuni, T. J . Chem. Soc.,
Chem. Commun. 1995, 221-222.
(17) Compounds 19a , 19b, 20a , and 20b each exist as a complex
mixture, presumably of anomers, the open-chain ketone, and rotamers.
As such, the ratio of anomers could not be determined.
(12) Moore, W. J .; Luzzio, F. A. Tetrahedron Lett. 1995, 36, 6599-
6602.

Synthesis of Glycosylated Amino Acids
J . Org. Chem., Vol. 66, No. 7, 2001 2321
Sch em e 5a
a
Reagents and conditions: (a) 14a or 14b, n-BuLi, TMEDA, THF, -78 °C, 1.5 h; 18, THF, -78 °C, 30 min; (b) 10% Pd/C, H2, ethyl
acetate/MeOH, rt, 24-48 h; (c) CSA, CH2Cl2, rt, 20 h; (d) TBAF, THF, rt, 2 h; (e) Ac2O, Pyr, rt, 10 h; (f) 10% Pd/C, H2, MeOH, Ac2O, rt,
20 h; (g) TFA, CH2Cl2, rt, 3 h; (h) Na2CO3, FmocCl, MeOH, rt, 30 min; (i) Dess-Martin periodinane, NaHCO3, CH2Cl2, rt, 30 min; (j)
NaClO2, NaH2PO4, 2-methyl-2-butene, t-BuOH, H2O, rt, 30 min.
In the optimal sequence, the alkyne was selectively
reduced to a cis-olefin by changing the hydrogenation
solvent to ethyl acetate/methanol (4:1 to 2:1) mixtures.
Using these solvent mixtures, the reaction rate was
substantially reduced, and hydrogenation was effectively
controlled to afford the desired olefin with no loss of the
trimethylsilyl group. To avoid reduction of the azide, the
reaction was interrupted before complete consumption
of the alkyne to give the desired olefins 20a (53%) and
20b (45%) along with the starting alkynes 19a (23%) and
19b (29%), respectively. The olefin was then separated
chromatographically, and the starting material was
recycled through the reaction conditions. With the cis-
olefin present, spiroketalization of 20a and 20b occurred
readily in the presence of catalytic camphorsulfonic acid
(CSA) to afford a single diastereomer of 21a or 21b (79%
and 51%, respectively).
It was next necessary to reduce both the olefin and the
azide. These two operations could be accomplished in a
single step by hydrogenation. However, reduction of the
azide was slowed by the bulky silyl protecting groups on
the sugar. Since silyl groups would not be ideally
compatible with peptide synthesis, they were removed
with fluoride and replaced with acetate groups to give
the triacetates 22a (90%, two steps) and 22b (85%, two
steps). The structures of the triacetates 22a and 22b were
unambiguously established by X-ray crystallography (see
the Supporting Information), which clearly shows the
desired configuration at the spiroketal carbon. Reduction
of the olefin and the azide was then successfully ac-
complished by hydrogenation of 22a and 22b with 10%
Pd/C in methanol in the presence of acetic anhydride to
afford the corresponding acetamides in 45% yield. The
low yield was attributed to the production of a byproduct
whose structure has not yet been determined.
removed under standard conditions and the resulting
amine was reprotected with an Fmoc group in a one-pot
procedure. The amino alcohols 23a and 23b were pro-
duced in 67% and 73% yield, respectively, using this one-
pot sequence. Dess-Martin oxidation18 followed by so-
dium chlorite oxidation19 gave the amino acids 24a (72%,
two steps) and 24b (79%, two steps), which are suitably
protected for Fmoc-based solid-phase peptide synthesis.
In summary, two conformationally constrained glyco-
conjugate analogues 2 and 3 were proposed and shown
to be reasonable conformational replacements for acces-
sible low energy conformations of the native glycosylated
amino acid by molecular modeling. These analogues were
synthesized in a convergent manner from L-methionine
and D-galactose. The synthesis included addition of an
acetylide anion to galactonolactone, followed by a ste-
reoselective spiroketalization. Analysis of the structural
ramifications of incorporating these units into peptides
and analysis of the binding properties of these con-
strained glycopeptides to protein targets are subjects of
ongoing research in this laboratory.
Exp er im en ta l Section
(4R,1′S)-3-ter t-Bu toxycar bon yl-2,2-dim eth yl-4-oxir an yl-
oxa zolid in e (12a ) a n d (4R,1′R)-3-ter t-Bu toxyca r bon yl-2,2-
d im eth yl-4-oxir a n yloxa zolid in e (12b). Dimethyldioxirane11
(84 mL, 0.097 M in acetone, 8.1 mmol) was added by addition
funnel to a solution of olefin 1110 (1.2 g, 5.4 mmol) in CH2Cl2
(30 mL) over 1 h. The reaction was protected from light by
wrapping in aluminum foil and allowed to stir at room
temperature overnight. The solvents were removed under
reduced pressure, and the resulting oil was suspended in Et2O.
The layers were separated, and the organic layer was dried
(18) Dess, B. D.; Martin, J . C. J . Am. Chem. Soc. 1991, 113, 7277-
7287.
To prepare for Fmoc-based peptide synthesis, the
acetonide and tert-butoxycarbonyl (Boc) groups were
(19) Lindgren, B. O.; Nilsson, T. Acta Chem. Scand. 1973, 27, 888-
890.

2322 J . Org. Chem., Vol. 66, No. 7, 2001
Koviach et al.
over Na2SO4, filtered, and concentrated. The crude epoxides
were separated by flash chromatography (SiO2, 6:1 hexanes/
EtOAc) to afford 12a as a colorless oil (856 mg, 3.52 mmol,
65%) and 12b as a white solid (248 mg, 1.02 mmol, 19%), each
as a mixture of rotamers. 12a : Rf 0.57 (SiO2, 3:1 hexanes/
EtOAc); [R]20D -14.1 (c 0.93, CHCl3); IR (thin film) 2981, 2934,
22 mmol) were added sequentially to a solution of 13a (6.8 g,
20 mmol) in THF (200 mL). The reaction mixture was stirred
at room temperature for 30 min. H2O and EtOAc were added,
the phases were separated, and the organic phase was washed
with brine. The combined aqueous phases were extracted with
EtOAc. The combined organic phases were dried over Na2SO4,
filtered and concentrated. The crude product was purified by
flash chromatography (SiO2, 3:1 hexanes/EtOAc) to afford the
pure desilylated alkyne, (1S,4′R)-1-(3′-tert-butoxycarbonyl-
2′,2′-dimethyloxazolidin-4′-yl)-1-hydroxybut-3-yne, as a color-
less oil and as a mixture of rotamers (5.2 g, 19 mmol, 97%):
Rf 0.33 (SiO2, 3:1 hexanes/EtOAc); [R]20D +7.5 (c 1.84, CHCl3);
IR (thin film) 3462, 2979, 2936, 2120, 1694 cm-1; 1H NMR (300
MHz, DMSO-d6, 90 °C) δ 3.8-4.0 (m, 4H), 2.57 (t, J ) 2.3 Hz,
1H), 2.29 (m, 2H), 1.50 (s, 3H), 1.45 (s, 12 H); 13C NMR (125
Hz, CDCl3, mixture of rotamers) δ 154.0, 94.3, 81.2, 80.5, 71.5,
70.6, 70.1, 64.6, 64.0, 61.3, 60.1, 28.3, 26.6, 23.9, 23.5; LRMS
m/z (CI) calcd for C14H24NO4 [M + H]+ 270, found 270; HRMS
m/z (EI) calcd for C13H20NO4 [M - CH3]+ 254.1392, found
254.1384.
N-Methyl-N-(trimethylsilyl)trifluoroacetamide (6.00 mL, 32.2
mmol) was added to a solution of the secondary alcohol
prepared above (5.76 g, 21.4 mmol) in CH3CN (50 mL). The
resulting solution was stirred at room temperature for 12 h.
Rotary evaporation followed by coevaporation with toluene
under low pressure (0.1 Torr) afforded crude 14a . Flash
chromatography (SiO2, 6:1 hexanes/EtOAc) afforded pure 14a
as a colorless oil and as a mixture of rotamers (7.31 g, 21.4
mmol, 100%): Rf 0.77 (SiO2, 3:1 hexanes/EtOAc); [R]20D +31.4
(c 1.54, CHCl3); IR (thin film) 2975, 2121, 1696 cm-1; 1H NMR
(300 MHz, DMSO-d6, 120 °C) δ 4.27 (ddd, J ) 3.0, 6.3, 6.3 Hz,
1H), 4.01 (dd, J ) 2.6, 7.4 Hz, 1H), 3.9 (m, 2H), 2.63 (m, 1H),
2.31 (m, 2H), 1.49 (s, 3H), 1.47 (s, 9H), 1.45 (s, 3H), 0.14 (s,
9H); 13C NMR (125 MHz, CDCl3, mixture of rotamers) δ 94.5,
93.8, 80.7, 80.0, 70.5, 68.5, 63.2, 62.6, 60.7, 60.3, 28.4, 26.6,
1698, cm-1 1H NMR (300 MHz, DMSO-d6, 120 °C) δ 3.91
;
(ABX, J ax ) 6.1 Hz, J bx ) 3.9 Hz, ∆ν ) 21.0 Hz, 2H), 3.61 (dt,
J ) 2.4 Hz, 6.3 Hz, 1H), 3.00 (ddd, J ) 2.4, 3,9, 6.6 Hz, 1H),
2.83 (dd, J ) 4.2, 5.1 Hz, 1H), 2.65 (dd, J ) 2.7, 5.1 Hz, 1H),
1.56 (s, 3H), 1.49 (s, 3H), 1.45 (s, 9H); 13C NMR (125 MHz,
CDCl3, mixture of rotamers) δ 152.2, 151.7, 94.3, 93.7, 80.3,
80.0, 66.0, 65.4, 59.2, 58.9, 52.2, 51.9, 48.2, 48.1, 28.3, 28.2,
27.4, 26.5, 24.2, 23.0; HRMS m/z (CI) calcd for C12H22NO4 [M
+ H]+ 244.1549, found 244.1564. Anal. Calcd for C12H21NO4:
C, 59.24; H, 8.70; N, 5.76. Found: C, 58.68; H, 8.32; N, 6.10.
12b: Rf 0.51 (SiO2, 3:1 hexanes/EtOAc); [R]20 +52.1° (c 1.00,
D
CHCl3); IR (thin film) 3059, 2980, 2935, 1698 cm-1; H NMR
1
(300 MHz, DMSO-d6, 140 °C) δ 4.07 (m, 1H), 3.92 (dd, J )
6.3, 9.3 Hz, 1H), 3.73 (dd, J )2.1, 9.3 Hz, 1H), 3.11 (m, 1H),
2.70 (t, J ) 4.5 Hz, 1H), 2.50 (m), 1.51 (s, 3H), 1.49 (s, 3H),
1.48 (s, 9H); 13C NMR (125 MHz, CDCl3, mixture of rotamers)
δ 153.2, 152.4, 94.8, 94.4, 81.3, 80.8, 63.8, 63.7, 57.1, 51.7, 44.8,
29.1, 27.7, 27.1, 25.0, 23.9; HRMS m/z (CI) calcd for C12H22
NO4 [M + H]+ 244.1549, found 244.1552. Anal. Calcd for
12H21NO4: C, 59.24; H, 8.70; N, 5.76. Found: C, 58.93; H,
-
C
8.60; N, 5.90.
(1S,4′R)-1-(3′-ter t-Bu toxyca r bon yl-2′,2′-d im eth yloxa zo-
lid in -4′-yl)-1-h yd r oxy-4-tr im eth ylsilylbu t-3-yn e (13a ). n-
BuLi (21.2 mL, 1.6 M in hexanes, 34 mmol) was added to a 0
°C solution of trimethylsilylacetylene (4.8 mL, 34 mmol) in
THF (65 mL). The resulting pale yellow solution was stirred
for 20 min. The solution was then cooled to -78 °C and added
by cannula to a -78 °C solution of epoxide 12a (5.5 g, 23 mmol)
in THF (225 mL). BF3‚OEt2 (8.3 mL, 68 mmol) was added, and
the reaction mixture was stirred for 1 h, at which time Et3N
(17 mL) was added. The solution was stirred for an additional
20 min at -78 °C before warming to room temperature. The
reaction mixture was concentrated, and flash chromatography
of the crude product (SiO2, 3:1 hexanes/EtOAc) afforded 13a
as a colorless oil and as a mixture of rotamers (6.9 g, 20 mmol,
26.3, 25.4, 24.9, 23.3, 0.23; LRMS m/z (EI) calcd for C17H31
-
NO4Si [M + H]+ 342, found 342; HRMS m/z (EI) calcd for
C
16H28NO4Si [M - CH3]+ 326.1788, found 326.1777. Anal.
Calcd for C17H31NO4Si: C, 59.79; H, 9.15; N, 4.10. Found: C,
59.85; H, 8.81; N, 4.25.
(1R,4′R)-1-(3′-ter t-Bu toxyca r bon yl-2′,2′-d im eth yloxa zo-
lid in -4′-yl)-1-tr im eth ylsilyloxybu t-3-yn e (14b). Compound
14b was prepared as described for 14a starting with TBAF
(12.5 mL, 1.0 M solution in THF, 12.5 mmol), acetic acid (0.35
mL, 6.2 mmol), and 13b (1.94 g, 5.67 mmol) in THF (50 mL).
The crude product was purified by flash chromatography (SiO2,
3:1 hexanes/EtOAc) to afford the pure desilylated alkyne,
(1R,4′R)-1-(3′-tert-butoxycarbonyl-2′,2′-dimethyloxazolidin-4′-
yl)-1-hydroxybut-3-yne, as a colorless oil and a mixture of
rotamers (1.4 g, 5.2 mmol, 91%): Rf 0.34 (SiO2, 3:1 hexanes/
90%): Rf 0.52 (SiO2, 3:1 hexanes/EtOAc); [R]20 +8.5 (c 1.04,
D
CHCl3); IR (thin film) 3466, 2977, 2176, 1701 cm-1; H NMR
1
(300 MHz, DMSO-d6, 45 °C) δ 5.07 (br s,1H), 3.99 (d, J ) 7.2
Hz, 1H), 3.8 (m, 3H), 2.35 (m, 2H), 1.48 (s, 3H), 1.43 (s, 12H),
0.11 (s, 9H); 13C NMR (125 MHz, CDCl3, mixture of rotamers)
δ 153.6, 151.7, 103.7, 102.7, 94.0, 87.0, 86.3, 80.7, 80.0, 71.0,
70.0, 64.4, 63.9, 61.3, 60.2, 28.1, 26.7, 25.9, 25.1, 24.0, 22.6,
-0.2.; LRMS m/z (CI) calcd for C17H32NO4Si [M + H]+ 342,
found 342; HRMS m/z (EI) calcd for C16H28NO4Si [M - CH3]+
326.1788, found 326.1794. Anal. Calcd for C17H31NO4Si: C,
59.79; H, 9.15; N, 4.10. Found: C, 59.82; H, 8.75; N, 3.99.
(1R,4′R)-1-(3′-ter t-Bu toxyca r bon yl-2′,2′-d im eth yloxa zo-
lidin -4′-yl)-1-h ydr oxy-4-tr im eth ylsilylbu t-3-yn e (13b). Com-
pound 13b was prepared as described for 13a starting from
n-BuLi (6.3 mL, 1.45 M in hexanes, 9.2 mmol) and trimeth-
ylsilylacetylene (1.3 mL, 9.2 mmol) in THF (20 mL), 12b (1.5
g, 6.2 mmol) in THF (60 mL), and BF3‚OEt2 (2.3 mL, 18.4
mmol). Flash chromatography of the crude product (SiO2, 6:1
hexanes/EtOAc) afforded 13b as a colorless oil and as a
mixture of rotamers (2.0 g, 5.8 mmol, 90%): Rf 0.52 (SiO2, 3:1
EtOAc); [R]20 +6.2 (c 1.30, CHCl3); IR (thin film) 3463, 2979,
D
2120, 1697 cm-1; 1H NMR (300 MHz, DMSO-d6, 60 °C) δ 5.01
(d, J ) 5.4 Hz, 1H), 3.8-4.0 (m, 4H), 2.62 (t, J ) 2.6 Hz, 1H),
2.24 (ABXY, J ax ) 2.9 Hz, J ay ) 2.9 Hz, J bx ) 7.4 Hz, J by ) 2.7
Hz, ∆ν ) 46.5 Hz, 2H), 1.52 (s, 3H), 1.44 (s, 9H), 1.39 (s, 3H);
13C NMR (125 MHz, CDCl3, mixture of rotamers) δ 154.7, 94.0,
81.2, 80.4, 70.8, 64.3, 61.0, 28.2, 27.0, 24.3, 24.0; LRMS m/z
(EI) calcd for C14H24NO4 [M + H]+ 270.2, found 270.2; HRMS
m/z (EI) calcd for C14H23NO4 [M]+ 269.1627, found 269.1624.
Anal. Calcd for C14H23NO4: C, 62.43; H, 8.61; N, 5.20. Found:
C, 62.71; H, 8.48; N, 4.80.
hexanes/EtOAc); [R]20 +13.4 (c 1.06, CHCl3); IR (thin film)
Compound 14b was prepared from N-methyl-N-(trimethyl-
silyl)trifluoroacetamide (1.60 mL, 8.63 mmol) and the second-
ary alcohol prepared above (2.00 g, 7.43 mmol) in CH3CN (20
mL). Flash chromatography (SiO2, 6:1 hexanes/EtOAc) af-
forded pure 14b as a colorless oil and a mixture of rotamers
(2.33 g, 6.82 mmol, 92%): Rf 0.83 (SiO2, 3:1 hexanes/EtOAc);
D
3475, 2977, 2176, 1701 cm-1; H NMR (300 MHz, DMSO-d6,
1
60 °C) δ 4.98 (app d, 1H), 3.97 (m, 2H), 3.87 (m, 2H), 2.32 (ABX,
J ax ) 4.5 Hz, J bx ) 7.2 Hz, ∆ν ) 46.1 Hz, 2H), 1.53 (s, 3H),
1.44 (s, 9H), 1.39 (s, 3H), 0.11 (s, 9H); 13C NMR (125 MHz,
CDCl3, mixture of rotamers) δ 154.8, 102.9, 93.9, 87.4, 81.2,
71.6, 64.5, 61.3, 28.3, 27.0, 26.1, 24.1, 0.0; LRMS m/z (ESI)
calcd for C17H32NO4Si [M + H]+ 342, found 342; HRMS m/z
[R]20 +15.6 (c 1.12, CHCl3); IR (thin film) 2977, 2122, 1704
D
cm-1
;
1H NMR (300 MHz, DMSO-d6, 90 °C) δ 4.22 (m, 1H),
(EI) calcd for
C
16H28NO4Si [M - CH3]+ 326.1788, found
3.99 (d, J ) 8.3 Hz, 1H), 3.9 (m, 2H), 2.60 (t, J ) 2.7 Hz, 1H),
2.27 (ABXY, J ax ) 3.2 Hz, J ay ) 3.1 Hz, J bx ) 8.4 Hz, J by ) 2.6
Hz, ∆ν ) 54.5 Hz, 2H), 1.53 (s, 3H), 1.46 (s, 9H), 1.41 (s, 3H),
0.15 (s, 9H); 13C NMR (125 MHz, CDCl3, mixture of rotamers)
δ 152.8, 152.2, 94.9, 94.1, 82.8, 82.7, 80.2, 70.1, 69.5, 69.3, 69.2,
63.1, 62.8, 60.7, 60.2, 28.6, 28.4, 26.8, 25.9, 23.8, 22.4, 22.1,
326.1780. Anal. Calcd for C17H31NO4Si: C, 59.79; H, 9.15; N,
4.10. Found: C, 60.15; H, 8.82; N, 4.02.
(1S,4′R)-1-(3′-ter t-Bu toxyca r bon yl-2′,2′-d im eth yloxa zo-
lid in -4′-yl)-1-tr im eth ylsilyloxybu t-3-yn e (14a ). TBAF (44
mL, 1.0 M solution in THF, 44 mmol) and acetic acid (1.3 mL,

Synthesis of Glycosylated Amino Acids
J . Org. Chem., Vol. 66, No. 7, 2001 2323
22.0, 0.4; LRMS m/z (ESI) calcd for C17H32NO4Si [M + H]+
342, found 342; HRMS m/z (ESI) calcd for C17H31NO4SiNa [M
+ Na]+ 364.1920, found 364.1928. Anal. Calcd for C17H31NO4-
Si: C, 59.79; H, 9.15; N, 4.10. Found: C, 60.12; H, 8.89; N,
4.04.
2-Azid o-3,4-d i-O-(ter t-bu tyld im eth ylsilyl)-6-O-(ter t-bu -
tyldiph en ylsilyl)-2-deoxy-D-galacton o-1,5-lacton e (18). KH-
MDS (23.4 mL, 0.50 M in toluene, 12 mmol) was added to a
-78 °C solution of lactone 17 (6.7 g, 11 mmol) in THF (100
mL). The reaction mixture was stirred for 45 min at -78 °C
and then cooled to -96 °C. Trisyl azide (3.3 g, 11 mmol) was
dissolved in THF (35 mL), cooled to -96 °C, and added by
cannula to the solution of the lactone enolate. The resulting
yellow mixture was stirred for 5 min at -96 °C. AcOH (1 mL)
was added, and the solution became bright yellow. The reaction
mixture was allowed to warm to room temperature over 1 h
at which time the color had dissipated. The solution was
concentrated under vacuum, and the crude product was
purified by flash chromatography (SiO2 pH 7.0, 20:1 hexanes/
EtOAc) to afford pure 18 as a white solid (4.0 g, 57 mmol,
1,5-An h ydr o-3,4-di-O-(ter t-bu tyldim eth ylsilyl)-6-O-(ter t-
bu tyldiph en ylsilyl)-2-deoxy-D-lyxo-h ex-1-en opyr an ose (16).
TBSOTf (12.4 mL, 54.0 mmol) was added dropwise to a 0 °C
solution of 1512 (7.0 g, 18 mmol) in anhyd pyridine (100 mL).
The resulting solution was stirred for 30 min at 0 °C and then
for 24 h at room temperature. The pyridine was removed by
coevaporation with toluene under reduced pressure (ca. 0.1
Torr). The resulting syrup was dissolved in CH2Cl2 (150 mL),
washed with saturated aqueous NaHCO3, H2O, and brine,
dried over Na2SO4, filtered, and concentrated. The crude
product was purified by flash chromatography (SiO2, 10:1
hexanes:Et2O) to afford pure 16 as an amorphous solid (10.5
56%): Rf 0.71 (SiO2, 8:1 hexanes/EtOAc); mp 84-86 °C; [R]20
D
+56.9 (c 1.36, CHCl3); IR (thin film) 2953, 2891, 2114, 1747
1
g, 17.1 mmol, 93%): Rf 0.83 (SiO2, 20:1 hexanes/EtOAc); [R]20
cm-1; H NMR (500 MHz, CDCl3) δ 7.6 (m, 4H), 7.5 (m, 2H),
D
-9.75 (c 1.11, CHCl3); IR (thin film) 2956, 2929, 1640 cm-1
;
7.4 (m, 4H), 4.22 (d, J ) 9.5 Hz, 1H), 4.21 (s, 1H), 3.98 (dd, J
) 6.4, 7.7 Hz, 1H), 3.84 (dd, J ) 8.2, 10.4 Hz, 1H), 3.76 (dd, J
) 5.9, 10.4 Hz, 1H), 3.68 (dd, J ) 1.6, 9.9 Hz, 1H), 1.05 (s,
9H), 0.94 (s, 9H), 0.83 (s, 9H), 0.17 (s, 3H), 0.164 (s, 3H), 0.161
(s, 3H), 0.10 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 168.1, 135.5,
132.8, 132.7, 130.1, 130.0, 127.9, 127.8, 79.8, 73.4, 69.4, 63.4,
61.2, 26.8, 26.0, 25.9, 19.1, 18.40, 18.35, -3.8, -4.1, -4.7, -5.1;
HRMS m/z (FAB) calcd for C34H56N3O5Si3 [M + H]+ 670.3528,
found 670.3539.
1H NMR (500 MHz, CDCl3) δ 7.65 (m, 4H), 7.3-7.4 (m, 6H),
6.10 (d, J ) 6.2 Hz, 1H), 4.55 (t, J ) 5.0 Hz, 1H), 4.02 (t, J )
3.7 Hz, 1H), 4.0 (m, 3H), 3.93 (dd, J ) 2.7, 11.2 Hz, 1H) 1.05
(s, 9H), 0.85 (s, 9H), 0.72 (s, 9H), 0.06 (s, 6H), -0.05 (s, 6H);
13C NMR (125 MHz, CDCl3) δ 142.6, 135.64, 135.59, 134.0,
129.43, 129.40 127.6, 127.5, 101.4, 79.5, 68.7, 65.0, 61.7, 26.9,
26.0, 25.9, 25.8, 19.3, 18.2, 18.1, -4.16, -4.52, -4.84, -4.94;
LRMS m/z (CI) calcd for C33H55O4Si3 [M - H]+ 611, found 611;
HRMS m/z (EI) calcd for C30H47O4Si3 [M - t-Bu]+ 555.2782,
found 555.2755.
(4′S,4′′R)-2-Azid o-1-C-[4′-(3′′-ter t-bu toxyca r bon yl-2′′,2′′-
dim eth yloxazolidin -4′′-yl)-4′-tr im eth ylsilyloxy-1′-bu tyn yl]-
3,4-d i-O-(ter t-bu tyld im eth ylsilyl)-6-O-(ter t-bu tyld ip h en -
ylsilyl)-2-deoxy-r,â-D-galactopyr an ose (19a). TMEDA (2.40
mL, 15.6 mmol) was added to a solution of 14a (2.7 g, 7.8
mmol) in THF (80 mL). The solution was cooled to -78 °C,
n-BuLi (5.0 mL, 7.8 mmol, 1.53 M in hexanes) was added, and
the resulting solution was stirred for 1.5 h. The lactone 18
(3.5 g, 5.2 mmol) was dissolved in THF (40 mL) and added to
the acetylide solution. The reaction mixture was stirred for
30 min, at which time TLC analysis indicated complete
disappearance of the lactone. Saturated aq NH4Cl was added,
and the reaction mixture was allowed to warm to room
temperature. EtOAc was added, and the phases were sepa-
rated. The organic layer was washed with H2O and brine. The
combined aq layers were extracted twice with EtOAc. The
combined organic layers were dried over Na2SO4, filtered, and
concentrated. Flash chromatography (SiO2, 10:1 hexanes/
EtOAc) afforded pure 19a as an amorphous solid and as
mixture of diastereomers and rotamers (4.0 g, 4.0 mmol,
77%): Rf 0.39 (SiO2, 8:1 hexanes/EtOAc); IR (thin film) 3416,
3,4-Di-O-(ter t -b u t yld im e t h ylsilyl)-6-O-(ter t -b u t yld i-
p h en ylsilyl)-2-d eoxy-D-ga la cton o-1,5-la cton e (17). PPh3‚
HBr (494 mg, 1.44 mmol) was added to a solution of 16 (8.8 g,
14 mmol) in THF (300 mL) and H2O (6.0 mL). The reaction
mixture was stirred for 6 h at room temperature. Aqueous
saturated NaHCO3 and CH2Cl2 were added, and the phases
were separated. The organic phase was washed with aqueous
saturated NaHCO3, dried over Na2SO4, filtered, and concen-
trated. The crude product was purified by flash chromatogra-
phy (SiO2, 10:1 hexanes/EtOAc) to afford 3,4-di-O-(tert-
butyldimethylsilyl)-6-O-(tert-butyldiphenylsilyl)-2-deoxy-D-
galactopyranose as a glass and a mixture of diastereomers (7.3
g, 12 mmol, 80%): Rf 0.36 (SiO2, 5:1 hexanes/EtOAc); IR (thin
film) 3440, 2928, 2857 cm-1; 1H NMR (500 MHz, CDCl3) δ 7.6
(m, 4H), 7.4 (m, 2H), 7.3 (m, 4H), 5.2 (s, 1H), 4.57 (d, J ) 9.3
Hz, 0.2H), 4.02 (d, J ) 10.1 Hz, 0.8H), 3.6-3.9 (m, 4.8H), 3.2
(app. t, 0.2H), 2.01 (ddd, J ) 3.2, 3.2, 12.1 Hz, 1H), 1.75-1.90
(m, 1H), 1.04 (s, 9H), 0.89 (s, 9H), 0.82 (s, 9H), 0.09 (s, 1H),
0.08 (s, 5H), 0.06 (s, 2H), 0.02 (s, 1H), 0.01 (s, 2H), -0.01 (s,
1H); 13C NMR (125 MHz, CDCl3) δ 135.6, 133.8, 133.7, 129.6,
127.6, 94.4, 92.5, 76.2, 72.8, 71.4, 70.4, 68.9, 67.9, 63.8, 63.1,
26.9, 26.2, 26.1, 18.5, 18.5, -3.8, -4.4, -4.7, -4.9; HRMS m/z
(EI) calcd for C34H57O5Si3 [M - H]+ 629.3514, found 629.3478.
NaOAc (5.7 g, 70 mmol) was added to a solution of the
galactopyranose prepared above (7.3 g, 12 mmol) in CH2Cl2
(200 mL). Molecular sieves (4 Å) and PCC (3.0 g, 14 mmol)
were added, and the reaction mixture was stirred for 1 h at
room temperature. Additional PCC (3.3 g, 15 mmol) was added,
and the reaction mixture was stirred for 1 h at room temper-
ature. The reaction mixture was filtered through SiO2 with
hexanes/EtOAc (5:1). Concentration afforded pure 17 as a
white solid (6.7 g, 11 mmol, 92%): Rf 0.47 (SiO2, 5:1 hexanes/
1
2953, 2892, 2218, 1688 cm-1; H NMR (300 MHz, DMSO-d6,
120 °C) δ 7.6 (m, 4H), 7.4 (m, 6H), 3.6-4.1 (m, 10H), 2.42 (m,
2H), 1.2-1.6 (m, 15H), 0.8-1.1 (m, 27H), 0.05-0.18 (m, 21H);
13C NMR (125 MHz, CDCl3) δ 135.7, 135.6, 133.8, 133.7, 129.5,
127.6, 127.5, 94.0, 93.7, 80.9, 80.3, 79.7, 74.2, 73.8, 69.0, 64.2,
62.9, 61.1, 60.4, 34.6, 31.6, 28.4, 27.0, 26.0, 25.9, 22.6, 19.2,
18.3, 18.2, 14.2, 14.1 0.3, -4.1, -4.4, -4.7, -4.8; MS m/z (FAB)
calcd for C51H90N5O9Si4 [M + NH4]+ 1029, found 1029.
(4′R,4′′R)-2-Azid o-1-C-[4′-(3′′-ter t-bu toxyca r bon yl-2′′,2′′-
dim eth yloxazolidin -4′′-yl)-4′-tr im eth ylsilyloxy-1′-bu tyn yl]-
3,4-d i-O-(ter t-bu tyld im eth ylsilyl)-6-O-(ter t-bu tyld ip h en -
ylsilyl)-2-d eoxy-r,â-D-ga la ctop yr a n ose (19b). Compound
19b was prepared as described for 19a starting with TMEDA
(0.45 mL, 3.0 mmol), 14a (500 mg, 1.5 mmol) in THF (15 mL),
n-BuLi (1.0 mL, 1.5 mmol, 1.45 M in hexanes), and the lactone
18 (670 mg, 1.0 mmol) in THF (1.0 mL). Flash chromatography
(SiO2, 10:1 hexanes/EtOAc) afforded pure 19b as an amor-
phous solid and as a mixture of diastereomers and rotamers
(623 mg, 0.62 mmol, 62%): Rf 0.58 (SiO2, 5:1 hexanes/EtOAc);
IR (thin film) 2930, 2857, 2218, 2113, 1704 cm-1; 1H NMR (300
MHz, DMSO-d6, 90 °C) δ 7.61 (m, 4H), 7.41 (m, 6H), 6.92 (m,
1H), 3.6-4.4 (m, 10H) 2.2-2.7 (m), 1.4-1.5 (m, 15H), 0.8-1.0
(m, 27H), -0.03-0.2 (m, 21H); 13C NMR (125 MHz, CDCl3,
mixture of rotamers) δ 153.0, 152.8, 135.7, 135.6, 133.4, 129.8,
129.7, 127.7, 127.6, 95.4, 94.7, 94.2, 91.7, 83.1, 80.8, 80.6, 80.4,
79.8, 73.6, 72.4, 71.4, 70.9, 68.8, 66.3, 62.8, 61.6, 60.6, 59.9,
28.6, 28.4, 26.9, 26.8, 26.3, 26.2, 26.13, 26.11, 26.0, 25.9, 25.7,
EtOAc); mp 94-95 °C; [R]20 -2.2 (c 1.11, CHCl3); IR (thin
D
film) 2956, 2930, 1742 cm-1; 1H NMR (500 MHz, CDCl3) δ 7.62
(m, 4H), 7.35-7.45 (m, 6H), 4.16 (s, 1H), 4.00 (t, J ) 6.9 Hz,
1H), 3.95 (ddd, J ) 1.8, 6.6, 10.0 Hz, 1H), 3.88 (dd, J ) 8.0,
10.3 Hz, 1H), 3.78 (dd, J ) 5.8, 10.4 Hz, 1H), 2.74 (dd, J )
10.9, 17.7 Hz, 1H), 2.61 (dd, J ) 6.5, 17.7 Hz, 1H), 1.06 (s,
9H), 0.91 (s, 9H), 0.83 (s, 9H), 0.14 (s, 3H), 0.10 (s, 3H), 0.09
(s, 6H); 13C NMR (125 MHz, CDCl3) δ 169.6, 135.5, 133.1,
132.9, 130.0, 129.9, 127.82, 127.75, 80.0, 68.9, 68.2, 61.7, 35.5,
26.8, 26.0, 25.9, 19.1, 18.39, 18.35, -4.0, -4.6, -4.8, -5.1;
LRMS m/z (CI) calcd for C34H56O5Si3 [M]+ 628, found 628;
HRMS m/z (EI) calcd for C33H53O5Si3 [M - CH3]+ 613.3201,
found 613.3177. Anal. Calcd for C34H56O5Si3: C, 64.42; H, 8.97.
Found: C, 64.42; H, 8.80.

2324 J . Org. Chem., Vol. 66, No. 7, 2001
Koviach et al.
22.5, 22.0, 19.1, 18.6, 18.5, 0.35, 0.28, 0.19, 0.09, -3.3, -3.8,
-3.9, -4.5, -4.6, -4.7; HRMS m/z (FAB) calcd for C51H86N4O9-
Si4Na [M + Na]+ 1033.537, found 1033.534.
(125 MHz, CDCl3, mixture of rotamers) δ 135.6, 133.6, 133.3,
130.9, 130.5, 130.1, 129.6, 127.7, 127.6, 127.1, 126.7, 97.1, 94.0,
93.6, 80.2, 73.6, 71.7, 69.4, 65.0, 64.8, 64.7, 63.1, 62.6, 60.3,
28.4, 27.5, 26.9, 26.2, 25.9, 24.4, 22.8, 19.2, 18.6, 18.5, -3.4,
-4.0, -4.8, -4.9. MS m/z (ESI) calcd for C48H78N4O8Si3Na [M
+ Na]+ 945.5025, found 945.5007.
(4′S,4′′R)-2-Azid o-1-C-[4′-(3′′-ter t-bu toxyca r bon yl-2′′,2′′-
d im eth yloxa zolid in -4′′-yl)-4′-tr im eth ylsilyloxy-1′-Z-bu te-
n yl]-3,4-d i-O-(ter t-bu tyld im eth ylsilyl)-6-O-(ter t-bu tyld i-
p h en ylsilyl)-2-d eoxy-r,â-D-ga la ctop yr a n ose (20a ). Pd/C
(10%, 200 mg) was added to a solution of 19a (3.0 g, 3.0 mmol)
in EtOAc (30 mL). The flask was evacuated (ca. 20 Torr),
refilled with H2 three times, and then stirred under H2 (690
Torr) for 72 h. The reaction mixture was filtered through
Celite, concentrated, and purified by flash chromatography
(SiO2, 10:1 hexanes/EtOAc) to afford 20a as an amorphous as
a mixture of anomers, the hydroxy ketone, and rotamers solid
(1.6 g, 1.6 mmol, 53%) and 19a (0.71 g, 0.71 mmol, 23%): Rf
0.56 (SiO2, 5:1 hexanes/EtOAc); IR (thin film) 3350, 2958, 2858,
(2R,3S,4R,5R,6S,8R,4′R)-5-Azid o-8-(3′-ter t-b u t oxyca r -
b on yl-2′,2′-d im et h yloxa zolid in -4′-yl)-3,4-d i-ter t-b u t yld i-
m et h ylsilyloxy-2-ter t-b u t yld ip h en ylsilyloxym et h yl-1,7-
d ioxa sp ir o[5.5]u n d ec-10-en e (21b). Compound 21b was
prepared as described for 21a , starting with CSA (18.0 mg,
0.076 mmol, 20 mol %) and 20b (382 mg, 0.377 mmol) in CH2-
Cl2 (6 mL). The reaction leading to 21b was carried out for 10
h. The crude product was purified by flash chromatography
(SiO2, 5:1 hexanes/EtOAc) to afford 21b as an amorphous solid
and as a mixture of rotamers (178 mg, 0.269 mmol, 51%): Rf
1
2109, 1695 cm-1; H NMR (300 MHz, DMSO-d6, 90 °C) δ 7.6
0.56 (SiO2, 5:1 hexanes/EtOAc); [R]20 +17.1 (c 1.80, CHCl3);
D
(m, 4H), 7.4 (m, 6H), 6.17 (s, 1H), 5.52 (br s, 2H), 4.0-4.2 (m,
2H), 3.8-4.0 (m, 3H), 3.7 (m, 1H), 3.64 (dd, J ) 5.4, 9.3 Hz,
1H), 3.55 (d, J ) 9.9 Hz, 1H), 2.7 (m, 1H), 2.25 (m, 1H), 1.45
(s, 3H), 1.42 (s, 9H), 1.37 (s, 3H), 1.05 (s, 9H), 0.97 (s, 9H),
0.88 (s, 9H), 0.05-0.18 (m, 21H); 13C NMR (125 MHz, CDCl3)
δ 196.0, 153.4, 152.4, 148.4, 135.6, 135.5, 134.6, 133.6, 133.5,
129.8, 129.6, 127.7, 127.6, 97.5, 94.3, 80.4, 80.1, 72.2, 71.9, 71.4,
68.8, 68.1, 65.9, 64.8, 64.5, 62.6, 62.0, 61.8, 60.8, 32.2, 28.4,
26.9, 26.3, 26.1, 22.6, 19.2, 18.6, 18.5, 14.1, 0.7, -3.5, -4.0,
-4.6, -4.7; MS m/z (ESI) calcd for C51H88N4O9Si4Na [M + Na]+
1035, found 1035.
IR (thin film) 2930, 2858, 2110, 1703 cm-1,1H NMR (300 MHz,
DMSO-d6, 75 °C, mixture of rotamers) δ 7.6 (m, 4H), 7.4 (m,
6H), 6.0-6.3 (m, 1H), 5.6 (d, J ) 10.3 Hz, 1H), 4.4 (m, 1H),
3.9-4.1 (m, 5H), 3.5-3.8 (m, 4H), 2.0 (m, 2H), 1.3-1.5 (m,
15H), 1.0 (s, 9H), 0.8-0.9 (m, 12H), -0.07-0.2 (m, 12H); 13C
NMR (125 MHz, CDCl3, mixture of rotamers) δ 152.1, 135.5,
133.4, 130.7, 129.7, 127.7, 127.1, 96.1, 94.1, 80.1, 73.3, 72.6,
72.1, 71.2, 67.0, 64.9, 63.7, 62.2, 59.4, 34.7, 31.6, 28.4, 26.9,
26.3, 26.0, 25.3, 23.2, 22.6, 19.2, 18.5, 14.1, -3.6, -3.9, -4.6,
-4.7; HRMS m/z (FAB) calcd for C48H78N4O8Si3Na [M + Na]+
945.5025, found 945.5007.
(4′R,4′′R)-2-Azid o-1-C-[4′-(3′′-ter t-bu toxyca r bon yl-2′′,2′′-
d im eth yloxa zolid in -4′′-yl)-4′-tr im eth ylsilyloxy-1′-Z-bu te-
n yl]-3,4-d i-O-(ter t-bu tyld im eth ylsilyl)-6-O-(ter t-bu tyld i-
ph en ylsilyl)-2-deoxy-r,â-D-galactopyr an ose (20b).Compound
20b was prepared as described for 20a starting with 10% Pd/C
(38 mg) and 19b (0.5 g, 0.5 mmol) in EtOAc/methanol (4:1, 15
mL). The reaction leading to 20b was carried out for 48 h and
purified by flash chromatography (SiO2,10:1 hexanes/EtOAc)
to afford 20b as an amorphous solid as a mixture of anomers,
the hydroxy ketone, and rotamers (225 mg, 0.222 mmol, 45%)
and 19b (146 mg, 0.144 mmol, 29%): Rf 0.53 (SiO2, 5:1
hexanes/EtOAc); IR (thin film) 3348, 2956, 2931, 2858, 2108,
(2R,3S,4R,5R,6S,8S,4′R)-2-Acetoxym eth yl-5-a zid o-8-(3′-
ter t-b u t oxyca r b on yl-2′,2′-d im et h yloxa zolid in -4′-yl)-3,4-
d ia cetoxy-1,7-d ioxa sp ir o[5.5]u n d ec-10-en e (22a ). TBAF
(2.8 mL, 2.8 mmol, 1.0 M in THF) was added to a solution
of 21a (794 mg, 0.860 mmol) in THF (10 mL). The reaction
mixture was stirred at room temperature for 2 h. H2O
(5 mL) and EtOAc (30 mL) were added, and the phases
were separated. The organic layer was washed with brine.
The combined aqueous layers were extracted with EtOAc.
The combined organic phases were dried over Na2SO4,
filtered, and concentrated. Flash chromatography (SiO2,
EtOAc) afforded the pure triol (2R,3R,4R,5R,6S,8S,4′R)-5-azido-8-
(3′-tert-butoxycarbonyl-2′,2′-dimethyloxazolidin-4′-yl)-3,4-
dihydroxy-2-hydroxymethyl-1,7-dioxaspiro[5.5]undec-10-ene as
a colorless oil and as a mixture of rotamers (352 mg, 0.772
1704, 1694 cm-1 1H NMR (500 MHz, DMSO-d6, mixture of
;
rotamers) δ 7.6 (m, 4H), 7.4 (m, 6H), 6.4 (m, 1H), 5.5 (m, 1H),
5.05 (m, 1H), 4.7 (m, 1H), 3.7-4.1 (m, 7H), 3.5 (m, 3H), 2.6
(m, 1H), 2.4 (m, 1H), 1.4 (m, 15H), 0.82-1.0 (m, 27H), 0.04-
0.16 (m, 21H); 13C NMR (125 MHz, CDCl3, mixture of rotam-
ers) δ 195.9, 152.7, 152.1, 135.6, 135.5, 134.0, 133.6, 131.9,
131.4, 129.7, 129.6, 127.7, 127.6, 127.5, 96.4, 96.2, 94.9, 94.1,
80.2, 73.9, 72.7, 72.2, 72.1, 71.1, 70.7, 70.1, 69.6, 68.1, 66.6,
65.1, 64.7, 63.1, 62.8, 61.9, 61.8, 61.1, 60.8, 60.5, 60.4, 59.7,
34.6, 32.4, 32.0, 31.6, 29.5, 28.7, 28.4, 26.9, 26.3, 26.1, 25.8,
25.5, 25.3, 24.0, 22.6, 19.5, 19.2, 18.6, 18.5, 18.4, 14.1, 0.43,
0.11, -3.4, -3.7, -3.8, -4.0, -4.2, -4.5, -4.7; MS m/z (FAB)
calcd for C51H88N4O9Si4Na [M + Na]+ 1035.553, found 1035.550.
(2R,3S,4R,5R,6S,8S,4′R)-5-Azid o-8-(3′-ter t-bu toxyca r bo-
n yl-2′,2′-dim eth yloxazolidin -4′-yl)-3,4-di-ter t-bu tyldim eth -
ylsilyloxy-2-ter t-bu tyld ip h en ylsilyloxym eth yl-1,7-d ioxa -
sp ir o[5.5]u n d ec-10-en e (21a ). CSA (4.0 mg, 0.017 mmol, 5
mol %) was added to a solution of 20a (346 mg, 0.342 mmol)
in CH2Cl2 (7 mL). The reaction mixture was stirred at room
temperature for 20 h. Saturated aqueous NaHCO3 and EtOAc
were added, and the phases were separated. The organic phase
was washed with brine. The combined aqueous phases were
extracted with EtOAc. The combined organic phases were
dried over Na2SO4, filtered, and concentrated. The crude
product was purified by flash chromatography (SiO2, 5:1
hexanes/EtOAc) to afford 21a as an amorphous solid and a
mixture of rotamers (248 mg, 0.269 mmol, 79%): Rf 0.65 (SiO2,
5:1 hexanes/EtOAc); [R]20D +64.2 (c 1.2, CHCl3); IR (thin film)
mmol, 90%): Rf 0.38 (SiO2, EtOAc); [R]20 +90.6 (c 1.01,
D
CHCl3); IR (thin film) 3419, 2977, 2866, 2109, 1701 cm-1; H
1
NMR (300 MHz, DMSO-d6, 105 °C) δ 6.06 (m, 1H), 5.56 (m,
1H), 4.06 (m, 2H), 3.9 (m, 4H), 3.76 (dd, J ) 6.7, 13.5 Hz, 1H),
3.57 (dd, J ) 6.9, 10.5 Hz, 1H), 3.44 (dd, J ) 5.6, 10.5 Hz,
1H), 3.29 (d, J ) 10.5 Hz, 1H), 1.9-2.1 (m, 2H), 1.48 (s, 3H),
1.44 (s, 3H), 1.43 (s, 9H); 13C NMR (125 MHz, CDCl3, mixture
of rotamers) δ 152.9, 152.2, 130.6, 130.3, 126.4, 97.4, 94.2, 93.9,
80.6, 80.4, 70.4, 70.0, 69.6, 68.7, 68.3, 67.6, 64.1, 63.3, 62.4,
61.9, 59.7, 28.2, 27.0, 24.4, 22.8; HRMS m/z (ESI) calcd for
C
20H32N4O8Na [M + Na]+ 479.2118, found 479.2125.
Pyridine (5 mL) and Ac2O (5 mL) were added to the triol
prepared above (352 mg, 0.772 mmol). The resulting solution
was stirred overnight at room temperature. Co-distillation
with toluene under high vacuum (2×, 0.1 Torr) gave crude 22a ,
which was purified by flash chromatography (SiO2, EtOAc) to
afford 22a as a white solid and as a mixture of rotamers (450
mg, 0.77 mmol, quant): Rf 0.24 (SiO2, 3:1 hexanes/EtOAc);
[R]20 +118.7 (c 0.9, CHCl3); IR (thin film) 2977, 2935, 2109,
D
1754, 1697 cm-1; 1H NMR (300 MHz, DMSO-d6, 120 °C) δ 6.22
(ddd, J ) 2.1, 6.0, 10.2 Hz, 1H), 5.75 (ddd, J ) 1.4, 2.6, 10.2
Hz, 1H), 5.3 (m, 2H), 4.28 (ddd, J ) 1.2, 6.0, 6.0 Hz, 1H), 4.1
(m, 3H), 3.9 (m, 3H), 3.63 (d, J ) 10.5 Hz, 1H), 2.2 (m, 1H),
2.12 (s, 3H), 2.05 (m, 1H), 2.00 (s, 3H), 1.98 (s, 3H), 1.55 (s,
3H), 1.49 (s, 3H), 1.46 (s, 9H); 13C NMR (125 MHz, CDCl3,
mixture of rotamers) δ 170.3, 170.1, 169.7, 169.6, 152.9, 152.1,
131.5, 131.1, 125.5, 125.4, 97.6, 97.4, 94.2, 93.9, 80.4, 70.3, 69.7,
68.4, 67.4, 65.2, 63.7, 61.5, 60.8, 59.8, 59.7, 58.6, 31.5, 28.4,
28.2, 27.4, 27.2, 27.0, 26.7, 24.6, 24.4, 22.7, 22.6, 20.6, 20.5,
14.0; HRMS m/z (ESI) calcd for C26H38N4O11Na [M + Na]+
605.2435, found 605.2433.
1
2955, 2887, 2108, 1702 cm-1; H NMR (300 MHz, DMSO-d6,
120 °C) δ 7.6 (m, 4H), 7.4 (m, 6H), 6.18 (ddd, J ) 1.8, 6.0, 9.9
Hz, 1H), 5.60 (dd, J ) 1.8, 9.9 Hz, 1H), 4.1 (m, 2H), 4.05 (m,
1H), 4.01 (t, J ) 6.3 Hz, 1H), 3.9 (m, 3H), 3.75 (m, 2H), 3.59
(d, J ) 9.9 Hz, 1H), 2.2 (m, 1H), 2.0 (m, 1H), 1.49 (s, 3H), 1.48
(s, 3H), 1.43 (s, 9H), 1.05 (s, 9H), 0.98 (s, 9H), 0.79 (s, 9H),
0.20 (s, 3H), 0.19 (s, 3H), 0.12 (s, 3H), -0.08 (s, 3H); 13C NMR

Synthesis of Glycosylated Amino Acids
J . Org. Chem., Vol. 66, No. 7, 2001 2325
(2R,3S,4R,5R,6S,8R,4′R)-2-Acetoxym eth yl-5-a zid o-8-(3′-
ter t-b u t oxyca r b on yl-2′,2′-d im et h yloxa zolid in -4′-yl)-3,4-
d ia cetoxy-1,7-d ioxa sp ir o[5.5]u n d ec-10-en e (22b). Com-
pound 22b was prepared as described for 22a starting with
TBAF (1.0 mL, 1.0 mmol, 1.0 M in THF) and 21b (183 mg,
0.198 mmol) THF (2.0 mL). Flash chromatography (SiO2,
EtOAc) afforded the pure triol (2R,3R,4R,5R,6S,8R,4′R)-5-
azido-8-(3′-tert-butoxycarbonyl-2′,2′-dimethyloxazolidin-4′-yl)-
3,4-dihydroxy-2-hydroxymethyl-1,7-dioxaspiro[5.5]undec-10-
ene as colorless oil and as a mixture of rotamers (78 mg, 0.17
(dd, J ) 7.4, 7.5 Hz, 2H), 5.60 (d, J ) 10.3 Hz, 1H), 5.32 (d, J
) 2.8 Hz), 5.28 (d, J ) 8.7 Hz, 1H), 5.04 (dd, J ) 2.9, 11.0 Hz,
1H), 4.46 (m, 1H), 4.41 (m, 1H), 4.32 (t, J ) 10.5 Hz, 1H), 4.19
(t, J ) 6.5 Hz, 1H), 4.1 (m, 4H), 3.9 (m, 1H), 3.7 (m, 3H), 2.14
(s, 3H), 2.01 (s, 3H), 1.96 (s, 6H), 1.6 (m, 6H); 13C NMR (125
MHz) δ 171.2, 171.0, 170.5, 170.3, 156.4, 143.8, 143.7, 141.3,
127.7, 127.0, 124.9, 120.0, 99.4, 69.5, 67.2, 66.6, 66.4, 62.1, 60.9,
55.4, 51.1, 47.3, 29.9, 28.3, 26.8, 23.4, 20.8, 17.9; HRMS m/z
(FAB) calcd for
683.2844.
C
35H42N2O12 [M + H]+ 683.2816, found
mmol, 85%): Rf 0.25 (SiO2, EtOAc); [R]20 +59.1 (c 1.20,
(2R,3S,4R,5R,6S,8R,2′R)-5-Aceta m ido-2-a cetoxym eth yl-
8-[2′-[(9H-flu or en -9-ylm eth oxy)ca r bon yl]a m in oeth a n ol]-
3,4-d ia cetoxy-1,7-d ioxa sp ir o[5.5]u n d eca n e (23b). Com-
pound 23b was prepared as described for 23a starting with
Ac2O (0.1 mL), 10% Pd/C (5 mg) and 22b (56 mg, 0.096 mmol)
in MeOH (1 mL). Flash chromatography (SiO2, EtOAc) of the
crude product afforded as a mixture of the 23b with the
corresponding olefin. The mixture was resubjected to hydro-
genation for 12 h, filtered through Celite, and concentrated to
afford (2R,3R,4S,5R,6R,8R,4′R)-5-acetamido-2-acetoxymethyl-
8-(3′-tert-butoxycarbonyl-2′,2′-dimethyloxazolidin-4′-yl]-3,4-di-
acetoxy-1,7-dioxaspiro[5.5]undecane as a colorless oil (26 mg,
0.043 mmol, 45%): Rf 0.54 (SiO2, EtOAc); [R]20D +23.8 (c 0.08,
MeOH); IR (thin film) 3400 (br), 2975, 2949, 1747, 1693, 1681,
1667 cm-1. 1H NMR (500 MHz, CDCl3) δ 5.73 (d, J ) 10.1 Hz,
1H), 5.30 (d, J ) 2.2 Hz, 1H), 5.05 (dd, J ) 2.8, 10.9 Hz, 1H),
4.30 (m, 2H), 3.88-4.12 (m, 6H), 2.13 (s, 3H), 2.04 (s, 3H), 1.96
(s, 3H), 1.94 (s, 3H), 1.6-1.8 (m, 6H), 1.51 (s, 3H), 1.47 (s, 3H),
1.45 (s, 3H); 13C NMR (125 MHz, CDCl3, mixture of rotamers)
δ 170.9, 170.6, 170.5, 170.4, 153.0, 100.5, 93.8, 80.8, 72.6, 69.2,
67.6, 66.9, 63.2, 62.4, 59.8, 51.9, 28.4, 26.9, 26.6, 23.9, 23.4,
20.8, 20.7, 20.6, 20.1, 13.7; HRMS m/z (FAB) calcd for
D
CHCl3); IR (thin film) 3402, 2926, 2854, 2110, 1697 cm-1; H
1
NMR (DMSO-d6, 300 MHz, 105 °C) δ 6.17 (ddd, J ) 3.4, 5.7,
9.6 Hz, 1H), 5.61 (d, J ) 9.8 Hz, 1H), 4.72 (m, 1H), 4.46 (m,
1H), 4.2 (m, 2H), 3.9-4.1 (m, 6H), 3.4-3.6 (m, 3H), 2.06 (m,
2H), 1.51 (s, 3H), 1.42 (m, 12H); 13C NMR (125 MHz, CDCl3,
mixture of rotamers) δ 152.9, 152.2, 131.3, 130.9, 126.6, 126.5,
96.4, 96.1, 94.3, 93.8, 80.6, 80.3, 72.9, 72.7, 70.8, 70.1, 69.8,
69.5, 66.1, 65.9, 63.9, 63.7, 62.3, 60.4, 60.0, 59.1, 52.6, 29.6,
28.3, 27.1, 26.7, 26.0, 24.4, 22.5; HRMS m/z (FAB) calcd for
calcd for C20H32N4O8 [M]+ 457.2298, found 457.2317.
Compound 22b was prepared starting with pyridine (51.5
mL), Ac2O (1.5 mL) and the triol prepared above (42 mg, 0.092
mmol). Flash chromatography (SiO2, EtOAc) afforded 22b as
a white solid and as a mixture of rotamers (57 mg, 0.097 mmol,
quant): Rf 0.20 (SiO2, 3:1 hexanes/EtOAc); [R]20D +44.9 (c 1.50,
1
CHCl3); IR (thin film) 2978, 2935, 2112, 1754, 1698 cm-1; H
NMR (300 MHz, DMSO-d6, 105 °C) δ 6.33 (m, 1H), 5.80 (dt, J
) 1.8, 10.2 Hz, 1H), 5.30 (m, 1H), 5.22 (dd, J ) 3.6, 10.8 Hz,
1H), 4.43 (m, 2H), 3.8-4.1 (m, 6H), 2.15 (m, 5H), 1.99 (s, 3H),
1.97 (s, 3H), 1.53 (s, 3H), 1.46 (s, 9H), 1.44 (s, 3H); 13C NMR
(125 MHz, CDCl3, mixture of rotamers) δ 170.3, 170.1, 170.0,
169.8, 152.8, 152.1, 132.4, 132.0, 131.8, 131.4, 125.9, 125.7,
96.3, 96.0, 94.3, 93.8, 80.4, 80.3, 74.4, 73.2, 70.3, 69.6, 67.6,
67.4, 63.9, 63.5, 63.2, 63.0, 61.8, 61.5, 60.7, 59.8, 58.9, 28.2,
27.1, 26.0, 24.7, 24.2, 23.3, 23.4, 20.6; HRMS m/z (FAB) calcd
for C26H38N4O11Na [M + Na]+ 605.2435, found 605.2439.
(2R,3S,4R,5R,6S,8S,2′R)-5-Aceta m id o-2-a cetoxym eth yl-
8-[2′-[(9H-flu or en -9-ylm eth oxy)ca r bon yl]a m in oeth a n ol]-
3,4-d ia cet oxy-1,7-d ioxa sp ir o[5.5]u n d eca n e (23a ). Ac2O
(0.1 mL) and 10% Pd/C (10 mg) were added to a solution of
22a (100 mg, 0.17 mmol) in MeOH (2 mL). The reaction
mixture was evacuated and refilled with H2 three times and
then stirred under a H2 atmosphere for 20 h, filtered through
Celite, and concentrated. Flash chromatography (SiO2, EtOAc)
of the crude product afforded (2R,3S,4R,5R,6S,8S,4′R)-5-
acetamido-2-acetoxymethyl-8-(3′-tert-butoxycarbonyl-2′,2′-di-
methyloxazolidin-4′-yl)-3,4-diacetoxy-1,7-dioxaspiro[5.5]-
undecane as a colorless oil (46 mg, 0.077 mmol, 45%): Rf 0.34
(SiO2, EtOAc); [R]20D +91.8 (c 0.27, MeOH); IR (thin film) 2934,
1749, 1692 cm-1; 1H NMR (500 MHz, CDCl3) δ 5.8 (br d, 1H),
5.34 (d, J ) 3.0 Hz, 1H), 5.15 (dd, J ) 3.5, 11.0 Hz, 1H), 4.31
(t, J ) 10.5 Hz, 1H), 4.1 (m, 3H), 3.9 (m, 4H), 2.13 (s, 3H),
2.03 (s, 6H), 1.96 (s, 3H). 1.95 (s, 3H), 1.6 (m, 12H), 1.46 (s,
9H); 13C NMR (125 MHz, CDCl3, mixture of rotamers) δ 170.8,
170.5, 170.3, 152.7, 99.1, 93.8, 80.5, 70.2, 69.5, 67.3, 67.0, 63.9,
62.0, 60.5, 51.2, 30.2, 28.3, 27.4, 27.0, 24.2, 23.5, 20.8, 20.7,
20.6, 17.7; HRMS m/z (EI) calcd for C28H44N2O12 [M]+ 600.2894,
found 600.2875.
C
28H44N2O12Na [M + H]+ 601.2973, found 601.2996.
Compound 23b was prepared starting with TFA (23 µL, 0.30
mmol), the compound prepared above (19 mg, 0.032 mmol) in
CH2Cl2 (0.5 mL), Na2CO3 (32 mg, 0.30 mmol), and FmocCl (8.0
mg, 0.03 mmol). Flash chromatography (SiO2, EtOAc) afforded
23b as a colorless oil (15 mg, 0.021 mmol, 73%): Rf 0.29 (SiO2,
95:5 EtOAc:MeOH), [R]20D +32.8 (c 0.18, MeOH); IR (thin film)
3370, 2928, 1754, 1726, 1664 cm-1; 1H NMR (500 MHz, CDCl3)
δ 7.74 (d, J ) 7.5 Hz, 2H), 7.58 (d, J ) 7.5 Hz, 2H), 7.37 (t, J
) 7.5 Hz, 2H), 7.29 (t, J ) 7.5 Hz, 2H), 6.1 (d, J ) 10.1 Hz,
1H), 5.32 (s, 1H), 5.18 (d, J ) 6.7 Hz, 1H), 5.10 (dd, J ) 3.0,
11.1 Hz, 1H), 4.45 (t, J ) 6.0 Hz, 2H), 4.31 (m, 2H), 4.20 (t, J
) 6.3 Hz, 2H), 4.11 (m, 1H), 4.03 (t, J ) 7.5 Hz, 2H), 3.76 (m,
2H), 2.14 (s, 3H), 1.97 (s, 3H), 1.93 (s, 6H), 1.5-1.8 (m, 6H);
13C NMR (125 MHz, CDCl3) δ 171.1, 170.6, 170.5, 170.5, 156.8,
143.8, 143.7, 141.4, 127.8, 127.1, 125.0, 120.0, 100.6, 71.7, 69.3,
67.3, 66.9, 62.2, 62.0, 55.2, 52.1, 47.3, 29.7, 27.4, 23.2, 20.82,
20.79, 20.6, 13.52; MS (FAB) calcd for C35H42N2O12 [M + H]+
683.2816, found 683.2844.
(2R,3S,4R,5R,6S,8S,2′R)-5-Aceta m id o-2-a cetoxym eth yl-
8-[2′-[(9H -flu or en -9-ylm et h oxy)ca r b on yl]-2′-a m in oa ce-
tic acid]-3,4-diacetoxy-1,7-dioxaspir o[5.5]u n decan e (24a).
Dess-Martin periodinane (13.5 mg, 0.032 mmol) and NaHCO3
(13.5 mg, 0.16 mmol) were added to a stirred solution of 23a
(20 mg, 0.029 mmol) in CH2Cl2 (1 mL). The resulting suspen-
sion was stirred for 1 h, at which time 10% aq Na2S2O3 and
EtOAc were added. The solution was stirred until clear (10
min), and the layers were separated. The aqueous phase was
extracted with EtOAc three times. The combined organic
phases were dried over Na2SO4, filtered, and concentrated. The
resulting solid was dissolved in EtOAc and filtered through a
small plug of SiO2. Concentration afforded the crude aldehyde,
which was used without further purification. The aldehyde as
prepared above was dissolved in t-BuOH/H2O (4:1, 0.5 mL),
and 2-methyl-2-butene (0.1 mL, 0.94 mmol), NaClO2 (17 mg,
0.19 mmol), and NaH2PO4 (13 mg, 0.91 mmol) were added
sequentially. The reaction mixture was stirred at room tem-
perature for 1 h, at which time H2O and EtOAc were added.
The phases were separated, and the aqueous phase was
extracted three times with EtOAc. The combined organic
phases were dried over Na2SO4, filtered, and concentrated to
afford a crude oil. Chromatography (SiO2, 95:5 EtOAc/HOAc)
afforded pure 24a as a yellow oil (15 mg, 0.021 mmol, 72%):
TFA (42 µL, 0.55 mmol) was added to a stirred solution of
the compound prepared above (33 mg, 0.055 mmol) in CH2Cl2
(0.5 mL). The reaction mixture was stirred for 3 h and
concentrated under reduced pressure. The crude amino alcohol
was dissolved in methanol, and Na2CO3 (58 mg, 0.55 mmol)
was added followed by FmocCl (14 mg, 0.055 mmol). The
resulting solution was stirred for 30 min. H2O and EtOAc were
added, and the phases were separated. The organic phase was
washed with brine, and the combined aqueous phases were
extracted with EtOAc. The combined organic phases were
dried over Na2SO4, filtered, and concentrated. Flash chroma-
tography (SiO2, EtOAc) afforded 23a as a colorless oil (25 mg,
0.037 mmol, 67%): Rf 0.38 (SiO2, 95:5 CH2Cl2/MeOH), [R]20
D
+60.7 (c 0.58, MeOH); IR (thin film) 3340, 2950, 1747, 1661
1
cm-1; H NMR (500 MHz, CDCl3) δ 7.74 (d, J ) 7.4 Hz, 2H),
7.57 (d, J ) 7.5 Hz, 2H), 7.38 (dd, J ) 7.4, 7.5 Hz, 2H), 7.30

2326 J . Org. Chem., Vol. 66, No. 7, 2001
Koviach et al.
Rf 0.20 (SiO2, 95:5 EtOAc/AcOH), [R]20D +49.8 (c 0.51, MeOH);
IR (thin film) 3372, 2919, 1745, 1664 cm-; 1H NMR (500 MHz,
CD3OD) δ; 7.80 (d, J ) 7.3 Hz, 2H), 7.67 (t, J ) 7.6 Hz, 2H),
7.39 (t J ) 7.4 Hz, 2H), 7.32 (t, J ) 7.3 Hz, 2H), 5.38 (s, 1H),
5.09 (d, J ) 11.3 Hz, 1H), 4.41 (t J ) 7.4 Hz, 1H), 4.21 (m,
3H), 4.10 (m, 3H), 3.92 (t, J ) 8.5 Hz), 2.13 (s, 3H), 1.99 (s,
3H), 1.96 (s, 3H), 1.93 (s, 3H), 1.5-1.7 (m, 6H). 13C NMR (125
MHz, CD3OD) δ 174.0, 172.3, 172.1, 158.5, 145.4, 145.3, 142.8,
129.0, 128.37, 126.35, 121.1, 101.0, 72.5, 70.7, 69.0, 68.4, 68.2,
63.2, 59.7, 52.3, 31.2, 27.9, 22.8, 20.8, 20.7, 20.7, 19.1; HRMS
m/z (FAB) calcd for C35H41N2O13 [M + H]+ 697.2609, found
697.2585.
1H), 2.12 (s, 3H), 1.99 (s, 6H), 1.96 (s, 3H), 1.5-1.7 (m, 6H).
13C NMR (125 MHz, CD3OD) δ 173.98, 172.38, 172.33, 172.01,
145.68, 145.52, 142.83, 129.08, 128.45, 126.32, 121.14, 101.49,
72.51, 70.60, 68.87, 68.80, 68.23, 63.01, 53.28, 30.67, 25.41,
22.74, 20.83, 20.71, 20.63, 15.00. HRMS m/z (FAB) calcd for
C
35H41N2O13 [M + H]+ 697.2609, found 697.2633.
Ack n ow led gm en t. This research was supported by
an NSF Career Award (CHE-9733765). R.L.H. also
thanks the Camille and Henry Dreyfus Foundation
(Camille Dreyfus Teacher-Scholar Award), Pfizer (J un-
ior Faculty Award), and Novartis (Young Investigator
Award) for support. This work was greatly facilitated
by a 500 MHz NMR spectrometer that was purchased
partly with funds from an NSF Shared Instrumentation
Grant (CHE-9523034). Bob Barkley (University of Colo-
rado) is thanked for obtaining mass spectra. Bruce Noll
(University of Colorado) is thanked for the determina-
tion of the X-ray crystal structures. Neil Whittemore is
thanked for performing the molecular modeling studies.
(2R,3S,4R,5R,6S,8R,2′R)-5-Aceta m id o-2-a cetoxym eth yl-
8-[2′-[(9H -flu or en -9-ylm et h oxy)ca r b on yl]-2′-a m in oa ce-
tic acid]-3,4-diacetoxy-1,7-dioxaspir o[5.5]u n decan e (24b).
Compound 24b was prepared as described for 24a starting
with Dess-Martin periodinane (10 mg, 0.023 mmol), NaHCO3
(10 mg, 0.12 mmol), and 23b (10.5 mg, 0.015 mmol) in CH2Cl2
(1 mL). Compound 24b was prepared from the crude aldehyde
prepared above, in t-BuOH/H2O (4:1, 0.5 mL) with 2-methyl-
2-butene (0.1 mL, 0.94 mmol), NaClO2 (8.5 mg, 0.094 mmol),
and NaH2PO4 (6.5 mg, 0.047 mmol). Flash chromatography
(SiO2, 95:5 EtOAc/HOAc) afforded 24b as a yellow oil (8.2 mg,
0.012 mmol, 79%): Rf 0.25 (SiO2, 95:5 EtOAc/AcOH), [R]20
D
Su p p or tin g In for m a tion Ava ila ble: Complete X-ray
crystallography data for compounds 12b, 22a , and 22b and
+33.6 (c 0.45, MeOH); IR (thin film) 3200-3550 br, 2923, 1744,
1736 cm-1, 1H NMR (500 MHz, CD3OD) δ 7.80 (d, J ) 7.5 Hz,
2H), 7.71 (d, J ) 7.1, Hz, 1H), 7.66 (d, J ) 7.5 Hz, 1H), 7.39 (t,
J ) 7.1 Hz, 2H), 7.34 (m, 2H), 5.32 (d, J ) 1.6 Hz, 1H), 5.18
(dd, J ) 3.2, 11.2 Hz, 1H), 4.47 (m, 2H), 4.35 (m, 1H), 4.25 (m,
2H), 4.15 (m, 1H), 4.10 (m, 2H), 3.94 (dd, J ) 6.9, 11.1 Hz,
1
photocopies of selected H and 13C NMR spectra. This informa-
tion is available free of charge via the Internet at
http://pubs.acs.org.
J O001512Z