Crich et al.
73.9, 73.4, 71.9, 69.9, 67.5, 66.8, 55.2, 27.5, 27.1, 27.0, 26.9, 22.6,
20.1; HRMS calcd for [C48H62O10SiNa]+ 849.4010, found 849.3991.
Methyl 6-O-(2-O-Benzyl-3,5-O-(di-tert-butylsilylene)-â-D-ara-
binofuranosyl)-2,3,4-tri-O-benzyl-r-D-glucopyranoside (17â). Col-
orless syrup; Rf 0.1 (CH2Cl2); [R]D -19.3 (c 0.9, CHCl3); 1H NMR
(500 MHz, CDCl3) δ 7.39-7.21 (m, 20 H), 5.01 (d, 1 H,
J ) 5.4 Hz), 4.97 (d, 1 H, J ) 10.9 Hz), 4.85 (d, 1 H, J ) 11.1
Hz), 4.81-4.76 (m, 3 H), 4.75 (d, 1 H, J ) 12.2 Hz), 4.65 (d, 1 H,
J ) 12.1 Hz), 4.60 (d, 1 H, J ) 11.1 Hz), 4.58 (d, 1 H, J ) 3.5
Hz), 4.28 (t, 1 H, J ) 9.1 Hz), 4.27 (dd, 1 H, J ) 5.0, 9.1 Hz),
3.98 (t, 1 H, J ) 9.3 Hz), 3.78 (br dd, 1 H, J ) 5.1, 10.0 Hz), 3.69
(dd, 1 H, J ) 5.3, 11.1 Hz), 3.60 (ddd, 1 H, J ) 5.0, 9.4, 10.4 Hz),
68.5, 63.9, 54.8, 54.7, 28.0, 27.5, 27.1, 26.4, 22.6, 20.1, 17.7. Owing
to the inseparable nature of this mixture of isomers it was partially
deprotected to 22 without further characterization. Compound 22
also was obtained in the form of an inseparable R,â-mixture. Rf
0.4 (CH2Cl2 EtOAc 3:1); HRMS calcd for [C22H32O9Na]+ 463.1944,
1
found 463.1943; H NMR (500 MHz, CDCl3) δ 7.40-7.30 (m, 5
H), 5.48 (d, 0.65 H, J ) 4.5 Hz, H1â), 5.21 (s, 0.35 H, H1R), 4.84
(s, 1 H, H1′), 4.80 (d, 0.65 H, J ) 11.7 Hz, â), 4.65 (d, 0.35 H,
J ) 11.7 Hz, R), 4.60 (d, 0.65 H, J ) 11.7 Hz, â), 4.55 (d, 0.35 H,
J ) 11.7 Hz, R), 4.37-4.31 (m, 1 H), 4.23 (dd, 0.65 H, J ) 5.8,
7.5 Hz, â), 4.13 (br d, 0.35 H, J ) 3.4 Hz, R), 5.78 (m, 1 H), 4.02
(dd, 0.35 H, J ) 5.5, 7.3 Hz, R), 3.92-3.89 (m, 1 H), 3.85-3.51
(m, 5 H), 3.36 (s, 1.95 H, â), 3.35 (s, 1.05 H, R), 1.54 (s, 3 H),
1.34 (s, 1.95 H, â), 1.33 (1.05 H, R), 1.30 (d, 1.95 H, J ) 6.3 Hz,
â), 1.25 (d, 1.05 H, J ) 6.1 Hz, R). 22R: 13C NMR (125 Hz,
CDCl3) δ 137.0, 128.6, 128.1, 127.9, 109.5, 105.2, 98.0, 87.6, 86.5,
76.9, 76.0, 75.6, 71.9, 64.9, 62.5, 54.9, 27.7, 26.4, 18.4. 22â: 13C
NMR (125 Hz, CDCl3) δ 137.7, 128.5, 128.1, 128.0, 109.4, 98.8,
97.9, 83.7, 81.3, 79.5, 77.8, 76.0, 73.7, 72.4, 63.7, 63.4, 54.8, 28.0,
26.3, 17.8.
3.53-3.48 (m, 2 H), 3.32 (s, 3 H), 1.05 (s, 9 H), 0.98 (s, 9 H); 13
C
NMR (125 Hz, CDCl3) δ 138.8, 138.4, 138.2, 138.0, 130.7, 128.8,
128.5, 128.4, 128.3, 128.1, 128.0, 127.9, 127.7, 127.6, 127.3, 101.0,
97.9, 82.1, 80.7, 79.9, 79.0, 77.9, 75.7, 74.9, 73.4, 73.4, 71.5, 70.3,
68.3, 67.4, 55.1, 47.0, 27.5, 27.2, 22.6, 20.1; HRMS calcd for
[C48H62O10SiNa]+ 849.4010, found 849.3983.
Methyl 4-O-(2-O-Benzyl-3,5-O-(di-tert-butylsilylene)-r-D-ara-
binofuranosyl)-2,3,6-tri-O-benzyl-r-D-glucopyranoside (19r).
Colorless syrup; Rf 0.15 (CH2Cl2); [R]D +30.5 (c 1.7, CHCl3); 1H
NMR (500 MHz, CDCl3) δ 7.32-7.21 (m, 20 H), 5.87 (d, 1 H,
J ) 3.0 Hz), 4.87 (d, 1 H, J ) 10.1), 4.82 (d, 1 H, J ) 10.1 Hz),
4.77 (d, 1 H, J ) 11.6 Hz), 4.75 (d, 1 H, J ) 10.8 Hz), 4.64 (d, 1
H, J ) 11.7), 4.60 (d, 1 H, J ) 9.9 Hz), 4.58 (br s, 1 H), 4.57 (d,
1 H, J ) 12.0 Hz), 4.48 (d, 1 H, J ) 11.9 Hz), 4.13-4.08 (m, 2
H), 3.99 (dd, 1 H, J ) 3, 7.2 Hz), 3.94 (t, 1 H, J ) 9.2 Hz), 3.89-
3.80 (m, 2 H), 3.77 (ddd, 1 H, J ) 1.7, 5.3, 10.0 Hz), 3.73 (dd, 1
H, J ) 1.9, 10.6 Hz), 3.67 (dd, 1 H, J ) 9.0, 9.8 Hz), 3.60 (dd, 1
H, J ) 5.6, 10.6 Hz), 3.49 (dd, 1 H, J ) 3.5, 9.7 Hz), 3.39 (s, 3
H), 1.06 (s, 9 H), 1.00 (s, 9 H); 13C NMR (125 Hz, CDCl3) δ 138.5,
138.2, 138.1, 137.6, 128.5, 128.3, 128.2, 128.2, 127.9, 127.7, 127.6,
127.5, 107.6, 97.9, 87.5, 81.9, 81.8, 79.8, 75.8, 75.5, 74.0, 73.7,
73.4, 71.7, 69.5, 69.4, 67.4, 55.2, 27.5, 27.2, 22.6, 20.1; HRMS
calcd for [C48H62O10SiNa]+ 849.4010, found 849.4035.
Methyl 4-O-(2-O-Benzyl-3,5-O-(di-tert-butylsilylene)-â-D-ara-
binofuranosyl)-2,3,6-tri-O-benzyl-r-D-glucopyranoside (19â). Col-
orless syrup; Rf 0.1 (CH2Cl2); [R]D -13.1 (c 0.8, CHCl3); 1H NMR
(500 MHz, CDCl3) δ 7.38-7.21 (m, 20 H), 5.01 (d, 1 H,
J ) 5.8 Hz), 4.92 (d, 1 H, J ) 10.6 Hz), 4.81 (d, 1 H, J ) 12.4
Hz), 4.81 (d, 1 H, J ) 10.3 Hz), 4.75 (d, 1 H, J ) 12.3 Hz), 4.70
(d, 1 H, J ) 12.2 Hz), 4.60 (d, 1 H, J ) 12.3 Hz), 4.56 (d, 1 H,
J ) 3.6 Hz), 4.51 (d, 1 H, J ) 12.1 Hz), 4.28-4.24 (m, 2 H), 4.11
(dd, 1 H, J ) 5.0, 9.2 Hz), 3.94 (m, 1 H), 3.85 (br d, 1 H, J ) 10.6
Hz), 3.75-3.71 (m, 3 H), 3.67-3.64 (m, 2 H), 3.47 (dd, 1 H, J )
3.5, 9.6 Hz), 3.44 (ddd, 1 H, J ) 5.0, 9.3, 10.5 Hz), 3.36 (s, 3 H),
1.06 (s, 9 H), 0.99 (s, 9 H); 13C NMR (125 Hz, CDCl3) δ 139.1,
138.3, 138.1, 137.8, 128.5, 128.4, 128.4, 128.2, 127.9, 127.8, 127.7,
127.6, 127.3, 102.2, 98.3, 80.2, 80.1, 79.6, 79.4, 79.3, 75.4, 73.6,
73.2, 72.8, 71.7, 70.0, 68.2, 68.1, 55.2, 27.6, 27.2, 22.6, 20.1; HRMS
calcd for [C48H62O10SiNa]+ 849.4010, found 849.4006.
Methyl 4-O-(2-O-Benzyl-D-arabinofuranosyl)-2,3-O-isopro-
pylidene-r-L-rhamnopyranoside (22). The arabinopyranoside 21
was obtained in the form of an inseparable R,â-mixture. Rf 0.3 (CH2-
Cl2); 1H NMR (500 MHz, CDCl3) δ 7.45-7.29 (m, 5 H), 5.47 (d,
0.65 H, J ) 5.0 Hz, H1â), 5.30 (s, 1 H, H1′), 5.14 (d, 0.35 H, J )
2.8 Hz, H1R), 4.87-4.77 (m, 3 H), 4.66 (d, 0.35 H, J ) 12.0 Hz,
R), 4.37-4.28 (m, 2 H), 4.22 (dd, 0.65 H, J ) 5.7, 7.4 Hz, â),
4.14 (dd, 0.35 H, J ) 5.7, 7.0 Hz, R), 4.11-4.02 (m, 1.65 H),
3.98-3.85 (m, 2.35 H), 3.74-3.60 (m, 2 H), 3.51 (dd, 0.65 H, J )
7.5, 10.0 Hz, â), 3.39 (d, 0.35 H, J ) 7.3, 9.9 Hz), 3.36 (s, 1.05 H,
R), 3.34 (s, 1.95 H, â), 1.52 (s, 1.95 H, â), 1.49 (s, 1.05 H, R),
1.35 (s, 1.95, â), 1.33 (s, 1.05 H, R), 1.26 (d, 1.95 H, J ) 6.6 Hz,
â), 1.25 (d, 1.05 H, J ) 6.4 Hz, R), 1.07 (s, 9 H), 1.00 (s, 3.15 H,
R), 0.98 (s, 5.85 H, â). 21R: 13C NMR (125 Hz, CDCl3) δ 137.7,
128.3, 127.9, 127.6, 127.3, 109.1, 106.8, 98.0, 81.6, 80.0, 78.4,
75.8, 73.8, 71.9, 67.6, 64.6, 54.7, 53.4, 27.9, 27.5, 27.1, 26.4, 22.6,
20.1, 17.7. 21â: 13C NMR (125 Hz, CDCl3) δ 137.9, 128.3, 127.9,
127.7, 109.3, 99.3, 97.9, 80.3, 78.4, 78.3, 78.1, 76.0, 74.0, 71.6,
Methyl 2-O-Benzyl-r-D-arabinofuranoside (23). Colorless
syrup; Rf 0.25 (hexanes-EtOAc 1:1); [R]D +60.5 (c 1, CHCl3),
lit.7 [R]D +60 (c 0.5, CHCl3); 1H NMR (500 MHz, CDCl3) δ 7.37-
7.28 (m, 5 H), 4.97 (s, 1 H), 4.63 (d, 1 H, J ) 11.6 Hz), 4.57 (d,
1 H, J ) 11.7 Hz), 4.13 (dd, 1 H, J ) 2.0, 4.0 Hz), 4.10 (dd, 1 H,
J ) 4.0, 7.5 Hz), 3.90 (d, 1 H, J ) 2.0 Hz), 3.82 (dd, 1 H, J ) 3.3,
11.9 Hz), 3.74 (dd, 1 H, J ) 4.3, 11.9 Hz), 3.38 (s, 3 H), 2.46 (br
s, 2 H); 13C NMR (125 Hz, CDCl3) δ 137.0, 128.6, 128.1, 127.9,
106.9, 87.5, 85.9, 75.4, 71.9, 62.4, 54.9.
p-Cresyl 2-O-Benzyl-3,5-O-(di-tert-butylsilylene)-1-thio-r-L-
arabinofuranoside (25). Compound 25 was prepared analogously
to its enantiomer 8, starting from L-arabinose. All spectral data
matched those of compound 8. [R]D -153.4 (c 1.0, CHCl3).
S-Phenyl 2-O-Benzyl-3,5-O-(di-tert-butylsilylene)-1-thio-r-L-
arabinofuranoside S-Oxide (26). Compound 24 (0.76 g) was
dissolved in CH2Cl2 (40 mL) and cooled to -78 °C under inert
atmosphere, and mCPBA (0.476 g, 70 wt %, ∼1.9 mmol, 1.2 equiv)
was added portionwise. The reaction mixture was warmed to room
temperature over 1 h, at which time TLC showed dissappearance
of starting material in favor of two significantly more polar
compounds. The sulfoxide 26 (0.621 g, 1.3 mmol, 79% yield) was
obtained as a mixture of diastereomers after column chromatography
on silica gel. Colorless syrup; Rf 0.19 and 0.28 (hexanes-EtOAc
1
10:1); H NMR (500 MHz, CDCl3) δ 7.59-7.64 (m, 4H), 7.48-
7.54 (m, 6H), 0.24-7.38 (m, 8H), 6.97-6.99 (m, 2H), 4.79 (d,
J ) 11.5 Hz, 1H), 4.69 (d, J ) 5.0 Hz, 1H), 4.63 (d, J ) 11.0 Hz,
1H), 4.62 (d, J ) 10.0 Hz, 1H), 4.60 (d, J ) 5.0 Hz, 1H), 4.55 (d,
J ) 11.0 Hz, 1H), 4.42 (dd, J ) 3.5, 7.5 Hz, 1H), 4.37 (dd, J )
5.5, 9.5 Hz, 1H), 4.31-4.33 (m, 1H), 4.21-4.29 (m, 3H), 4.05-
4.10 (m, 1H), 3.84-3.92 (m, 3H), 1.06 (s, 18H), 1.01 (s, 9H), 0.96
(s, 9H); 13C NMR (125 Hz, CDCl3) δ 139.8, 139.6, 137.2, 131.6,
131.1, 129.19, 129.15, 128.4, 128.3, 128.2, 128.1, 128.0, 127.9,
127.7, 125.5, 124.4, 99.4, 98.2, 82.1, 81.5, 81.1, 78.5, 77.1, 76.7,
76.6, 72.3, 71.9, 67.3, 67.2, 27.4, 27.1, 27.0, 22.6, 20.2, 20.0; HRMS
calcd for [C26H36O5SSiNa]+ 511.1945, found 511.1955.
Activation of Sulfoxide 26 with Trifluoromethanesulfonic
Anhydride (Method G). Donor 26 (1.0 equiv) and TTBP (2.0
equiv) were dissolved in dry CH2Cl2 (0.04 M) together with crushed
4Å molecular sieves under argon and cooled to -78 °C. Tf2O (1.2
equiv) was added and the solution was allowed to stir for ∼10
min, before being warmed to -50 °C for ∼15 min and subsequently
recooled to -78 °C. The acceptor (0.63 equiv) in CH2Cl2 (0.1 M)
was then added dropwise. The reaction mixture was allowed to
warm to -30 °C, when it was quenched by addition of Et3N and
filtered through Celite. The solvent was removed and the crude
mixture directly purified by column chromatography on silica gel.
Modified Method for Activation of Sulfoxide 26 with Tri-
fluoromethanesulfonic Anhydride (Method H). All conditions
and equivalents for method H are the same as those employed in
1564 J. Org. Chem., Vol. 72, No. 5, 2007