CH(CO2Et)2), 4.23 (1H, s, OH), 3.94–3.86 (4H, m, 2 ×
OCH2CH3), 3.78 (1H, dd, J 1.7, 1.5, C(3)H), 3.71 (1H, dd, J
2.7, 1.5, C(4)H), 3.53 (1H, dd, J 12.1, 4.3, C(6)HaHb), 2.89 (3H,
s, OCH3), 1.20 (9H, s, C(CH3)3), 1.08 (9H, s, C(CH3)3),
0.89–0.83 (6H, m, 2 × CH2CH3); δC (C6D6, 125 MHz) 168.4
(CvO), 167.2 (CvO), 82.7 (C(1)H), 81.6 (C(5)H), 74.0 (C(3)H),
70.3 (C(2)H), 67.3 (C(4)H), 62.6 (C(6)H2), 62.4 (CH2CH3),
62.3 (CH2CH3), 57.7 (OCH3), 52.8 (CH(CO2Et)2), 28.4
(C(CH3)3), 28.3 (C(CH3)3), 21.6 (C(CH3)3), 21.2 (C(CH3)3),
13.7 (2 × CH2CH3); m/z (FAB+) 531 (MNa+, 6%), 329 (23), 217
(90), 176 (100); HRMS expected MNa+ (C22H40NaO9SSi)
531.2060, found 531.2068.
d, J 8.0, C(5)H), 4.17 (1H, app q, J 2.4, C(2)H), 4.03 (1H, d, J
13.1, SCHaHb), 3.82 (1H, app q, J 2.5, C(4)H), 3.49–3.67 (2H,
m, CvOCH2), 2.72 (1H, dd, J 13.1, 8.0, SCHaHb), 2.29 (3H, s,
CH3CvO), 1.15 (9H, s, C(CH3)3), 1.07 (9H, s, C(CH3)3); enol
form (selected peaks) 11.57 (1H, s, OH), 5.32 (1H, m, C(3)H),
4.97 (1H, s, CHvC), 4.20 (1H, app q, J 2.4, C(2)H), 3.95 (1H,
d, J 12.8, SCHaHb), 3.80 (1H, app q, J 2.5, C(4)H), 2.01 (3H, s,
CH3CvO), 1.16 (9H, s, C(CH3)3), 1.08 (9H, s, C(CH3)3); δC
(CDCl3, 125 MHz) keto form 199.5 (CvO ketone), 164.3
(CvO ester), 102.2 (C(1)H), 79.9 (C(5)H), 68.6 (C(4)H), 67.7
(C(3)H), 67.1 (C(2)H), 59.9 (SCH2), 49.5 (CH2CvO), 30.6
(CH3CvO), 29.3 (C(CH3)3), 27.9 (C(CH3)3), 22.2 (C(CH3)3),
21.5 (C(CH3)3); m/z (CI+, CH4) 419 (MH+, 18%), 361 ([M −
tBu]+, 10), 335 (15), 259 (35), 85 (100); HRMS expected MH+
(C18H31O7SSi) 419.1560, found 419.1551.
Ethoxycarbonylmethyl
6-bromo-1,6-dideoxy-2,4-O-(di-tert-
butylsilane-1,1-diyl)-3-O-methyl-1-thio-β-D-glucopyranoside (17).
Ethyl bromoacetate (16 μL, 150 μmol) was added to a solution
of silylene bisether 13 (50 mg, 150 μmol) in MeCN (0.3 mL),
and the mixture was stirred for 10 h at room temperature. The
resulting black precipitate was removed by filtration through
Celite® and the filtrate was concentrated in vacuo. Column
chromatography (Florisil®; EtOAc–petrol 5 : 95) afforded
bromide 17 (54 mg, 72%) as a colourless oil; [α]2D0 = −59.5 (c
1.50, CH2Cl2); νmax (CHCl3 cast)/cm−1 2980m, 1747s, 1691s,
1421s, 1265s; δH (CDCl3, 500 MHz) 5.37 (1H, t, J 1.0, C(1)H),
4.38 (1H, dd, J 3.8, 2.4, C(4)H), 4.34 (1H, ddd, J 3.7, 2.5, 1.0,
C(3)H), 4.23 (1H, ddd, J 9.0, 6.7, 3.8, C(5)H), 4.17 (2H, q,
J 7.1, CH2CH3), 4.09 (1H, dd, J 10.3, 9.0, C(6)HaHb), 3.96 (1H,
dd, J 10.3, 6.7, C(6)HaHb), 3.95 (1H, dd, J 3.7, 1.0, C(2)H),
3.52 (1H, d, J 14.7, CHaHbS), 3.48 (3H, s, OCH3), 3.28 (1H, d,
J 14.7, CHaHbS), 1.26 (3H, t, J 7.1, CH2CH3), 1.04 (9H, s,
C(CH3)3), 1.02 (9H, s, C(CH3)3); δC (CDCl3, 125 MHz) 170.6
(CvO), 82.7 (C(1)H), 78.6 (C(5)H), 74.1 (C(2)H), 69.0 (C(3)H),
66.5 (C(4)H), 61.4 (CH2CH3), 58.4 (OCH3), 34.3 (CH2S), 33.3
(C(6)H2), 28.1 (C(CH3)3), 28.0 (C(CH3)3), 21.5 (C(CH3)3), 21.2
(C(CH3)3), 14.1 (CH2CH3); m/z (FAB+) 523/521 (MNa+,
43/45%), 500/498 (19/31), 411 (35), 321 (100); HRMS expected
MNa+ (C19H3579BrNaO6SSi) 521.1005, found 521.1010.
To a stirred suspension of this sulfoxide (140 mg, 0.33 mmol)
in MeCN (5 mL) and p-carboxybenzenesulfonylazide (80 mg,
0.351 mmol), cooled to 0 °C, was added triethylamine (116 μL,
0.84 mmol). The mixture was allowed to warm to room tempera-
ture and stirred for 60 h. The solvent was removed in vacuo, and
the solid residue was dissolved in Et2O (50 mL). This solution
was washed with H2O (30 mL), sat. aq. NaHCO3 (30 mL) and
brine (30 mL), dried (Na2SO4), filtered and concentrated in
vacuo to afford the title compound 33 as a cream solid (130 mg,
88%), which was used without further purification; mp
172–173 °C; [α]2D0 = −29.5 (c 0.56, CHCl3); (found: C, 48.75;
H, 6.45; N, 5.9. Calc. for C18H28N2O7SSi: C, 48.6; H 6.35; N,
6.30%); νmax/cm−1 (CHCl3 cast) 2940m, 2862m, 1726s, 1663s,
1322s, 1110s, 1067 vs., 1038s, 1000s, 824s, 768s; δH (CDCl3,
500 MHz) 5.41 (1H, m, C(3)H), 5.27 (1H, s, C(1)H), 5.21 (1H,
d, J 8.0, C(5)H), 4.26 (1H, m, C(2)H), 3.86 (1H, m, C(4)H),
3.82 (1H, d, J 13.2, SCHaHb), 2.81 (1H, dd, J 13.2, 8.0,
SCHaHb), 2.45 (3H, s, CH3CvO), 1.16 (9H, s, C(CH3)3), 1.08
(9H, s, C(CH3)3); δC (CDCl3, 125 MHz) 188.7 (CvO), 159.3
(CvO), 102.2 (C(1)H), 79.7 (C(5)H), 74.9 (CvN2), 68.8 (C(4)H),
68.1 (C(3)H), 67.0 (C(2)H), 59.5 (SCH2), 29.3 (C(CH3)3), 28.2
(CH3CvO), 27.9 (C(CH3)3), 22.2 (C(CH3)3), 21.5 (C(CH3)3);
m/z (CI+, CH4) 445 (MH+, 40%), 417 (18), 387 (22), 335 (30),
317 (35), 259 (75), 85 (100); HRMS expected MH+
(C18H29N2O7SSi) 445.1465, found 445.1455.
1-Deoxy-3-O-(2-diazo-3-oxobutanoyl)-2,4-O-(di-tert-butylsilane-
1,1-diyl)-1-thio-1,6-anhydro-D-glucopyranose (S)-S-oxide (33).
To a stirred solution of acetoacetate 20 (49 mg, 0.12 mmol) in
CH2Cl2 (1.5 mL) was added m-chloroperbenzoic acid (70–75%
purity, 30 mg, 0.12 mmol) followed by sat. aq. NaHCO3
(0.5 mL). The resulting mixture was stirred at room temperature
for 1.5 h, then further m-chloroperbenzoic acid (70–75% purity,
5 mg) was added and the mixture stirred for a further 15 min.
Water (10 mL) was added and the organic material extracted
with CH2Cl2 (3 × 15 mL). The combined organic extracts were
washed with sat. aq. NaHCO3 (20 mL) and brine (20 mL), dried
(MgSO4), filtered and concentrated in vacuo. Column chromato-
graphy (SiO2, EtOAc) afforded 1-deoxy-3-O-(3-oxobutanoyl)-
2,4-O-(di-tert-butylsilane-1,1-diyl)-1-thio-1,6-anhydro-D-gluco-
pyranose (S)-S-oxide as a white solid (41 mg, 80%), as a
3.3 : 1 mixture of keto:enol forms by NMR; mp 177–179 °C;
[α]2D0 = −79.3 (c 0.58, CHCl3); (found: C, 51.3; H, 7.3; S, 7.6.
Calc. for C18H30O7SSi: C, 51.65; H, 7.2; S, 7.7%); νmax(solid)/
cm−1 2939m, 2861m, 1753s, 1717s, 1259s, 1151s, 1108s,
1055s, 1029vs, 981s, 825s, 789s, 764s; δH (CDCl3, 500 MHz)
keto form 5.34 (1H, m, C(3)H), 5.22 (1H, s, C(1)H), 5.16 (1H,
(1S,2S,6R,8S,10S,11R)-5-Acetyl-13,13-di-tert-butyl-3,9,12,14-tet-
raoxa-6-oxo-6-thia-13-silatetracyclo[6.6.0.02,11.06,10]tetradecan-6-
ium-5-id-4-one (34). To a stirred solution of diazoester 33
(111 mg, 0.250 mmol) in CH2Cl2 (3 mL) under argon was
added rhodium acetate dimer (1.6 mg), and the resulting mixture
heated to reflux for 1 h. The solution was allowed to cool to
room temperature and then concentrated in vacuo. Recrystallisa-
tion from CH2Cl2/petrol afforded the title compound 34 as a
white fluffy solid (46 mg); a second crop from EtOAc/petrol
gave identical material (19 mg, total 65 mg, 63%); mp
217–218 °C (CH2Cl2/petrol); [α]2D0 = +45.1 (c 0.89, CHCl3);
(found: C, 51.6; H, 6.8; S, 7.5. Calc. for C18H28O7SSi: C, 51.9;
H, 6.8; S, 7.7%); νmax(CHCl3 cast)/cm−1 2938m, 2861m, 1714s,
1638s, 1123s, 1110s, 1058s; δH (CDCl3, 500 MHz) 5.32 (1H, br
s, C(10)H), 5.14 (1H, dd, J 7.5, 1.6, C(8)H), 4.92 (1H, t, J 3.1,
C(2)H), 4.65 (1H, app. td, J 2.8, 2.4, C(11)H), 4.55 (1H, d, J
11.8, C(7)HaHb), 4.15 (1H, app. dt, J 3.1, 2.2, C(1)H), 3.67 (1H,
dd, J 11.8, 7.5, C(7)HaHb), 2.42 (3H, s, CH3CvO), 1.12 (9H, s,
8624 | Org. Biomol. Chem., 2012, 10, 8616–8627
This journal is © The Royal Society of Chemistry 2012