Notes
J . Org. Chem., Vol. 61, No. 17, 1996 6081
SiK m/ e (M + K) 461.1762, found 461.1757; 1H NMR (270 MHz,
CDCl3): (R-for m ) δ 0.12 (6H, s, TBDMS Si-Me), 0.92 (9H, s,
TBDMS Si-tBu), 1.31 (3H, s, isopropylidene-CH3), 1.38 (3H, s,
isopropylidene-CH3), 3.45 (1H, bs, 1 or 4-OH), 3.72 (1H, m, 5-Ha),
3.94 (1H, m, 5-Hb), 4.15 (1H, m, 4-H), 4.21 (1H, m, 3-H), 4.72
(1H, bs, 1 or 4-OH), 5.06 (1H, m, 1-H), 6.72 (1H, s, benzofuran
3′-H), 7.19-7.28 (2H, m, benzofuran 5′-H, 6′-H), 7.48-7.62 (2H,
m, benzofuran 4′-H, 7′-H). Anal. Calcd for C22H34O6Si: C, 62.53;
H, 8.11. Found: C, 62.63; H, 8.22.
Red u ctive Am in a tion of 7 to give Aza su ga r 8. Typ ica l
P r oced u r e. Ammonium formate (3 mmol), NaBH3CN (3 mmol),
powdered molecular sieves (3A) (100 mg), and 7 were dissolved
in MeOH (10 mL). After stirring for 18 h at room temperature,
the reaction mixture was filtrated through Celite (Wako hyflo
super-cell), extracted with chloroform, and dried over Na2SO4.
The solvent was removed, and the residue was purified by pTLC
(AcOEt/hexane, 1/3) to give 8.
5-O-(ter t-Bu tyld im eth ylsilyl)-1,4-d id eoxy-1,4-im in o-2,3-
O-isop r op ylid en e-1-(2-th ien yl)-D-r ibitol (8a ): oil; IR (neat)
840, 1080, 1250, 1370, 1780, 2900 cm-1; HRMS (FAB, NBA)
calcd for C18H32O3NSSi m/ e (M + H) 370.1872, found 370.1880;
1H NMR (500 MHz, CDCl3) (â-form) δ 0.08 (6H, s, TBDMS Si-
Me), 0.91 (9H, s, TBDMS Si-tBu), 1.30 (3H, s, isopropylidene-
CH3), 1.53 (3H, s, isopropylidene-CH3), 1.91 (1H, bs, N-H), 3.04
(1H, ddd, 4-H, J 3,4 ) 4.4 Hz, J 4,5a ) 6.9 Hz, J 4,5b ) 5.8 Hz), 3.83
(1H, dd, 5-Ha, J 4,5a ) 6.9 Hz, J gem ) 9.9 Hz), 3.93 (1H, dd, 5-Hb,
J 4,5b ) 5.8 Hz, J gem ) 9.9 Hz), 4.21 (1H, d, 1-H, J 1,2 ) 4.1 Hz),
4.65 (1H, dd, 2-H, J 1,2 ) 4.1 Hz, J 2,3 ) 5.5 Hz), 4.69 (1H, dd,
3-H, J 2,3 ) 5.5 Hz, J 3,4 ) 4.4 Hz), 6.97 (1H, m, thiophene 4′-H),
7.05 (1H, m, thiophene 3′-H), 7.26 (1H, m, thiophene 5′-H). Anal.
Calcd for C18H32O3NSSi: C, 58.33; H, 8.71; N, 3.78. Found: C,
58.16; H, 8.89; N, 3.55.
1-(2-Ben zofu r yl)-5-O-(ter t-bu tyldim eth ylsilyl)-1,4-dideoxy-
1,4-im in o-2,3-O-isop r op ylid en e-D-r ibitol (8b): oil; IR (neat)
830, 1070, 1240, 1420, 1780, 2890 cm-1; HRMS (FAB, NBA)
calcd for C22H34O4NSi m/ e (M+H) 404.2257, found 404.2260;
1H NMR (270 MHz, CDCl3): (â-form) δ 0.11 (6H, s, TBDMS Si-
Me), 0.92 (9H, s, TBDMS Si-tBu), 1.30 (3H, s, isopropylidene-
CH3), 1.44 (3H, s, isopropylidene-CH3), 1.90 (1H, bs, NH), 3.08
(1H, ddd, 4-H, J 3,4 ) 4.3 Hz, J 4,5a ) 6.6 Hz, J 4,5b ) 6.3 Hz), 3.89
(1H, dd, 5-Ha, J 4,5a ) 6.6 Hz, J gem ) 9.9 Hz), 3.96 (1H, dd, 5-Hb,
J 4,5b ) 6.3 Hz, J gem ) 9.9 Hz), 4.09 (1H, d, 1-H, J 1,2 ) 4.0 Hz),
4.73 (1H, dd, 2-H, J 1,2 ) 4.0 Hz, J 2,3 ) 5.6 Hz), 4.87 (1H, dd,
3-H, J 2,3 ) 5.6 Hz, J 3,4 ) 4.3 Hz), 6.72 (1H, s, benzofuran 3′-H),
7.17-7.54 (4H, m, benzofuran 4′-H, 5′-H, 6′-H, 7′-H). Anal.
Calcd for C22H34O4NSi: C, 65.31; H, 8.47; N, 3.46. Found: C,
65.52; H, 8.43; N, 3.53.
5-O-(ter t-Bu tyld im eth ylsilyl)-1,4-d id eoxy-1,4-im in o-2,3-
O-isop r op ylid en e-1-[2-[N-(p h en ylsu lfon yl)in d olyl]]-D-r ibi-
tol (8c): foam; IR (KBr) 840, 1200, 1380, 1440, 1620, 1720, 2900
cm-1; HRMS (FAB, NBA) calcd for C28H37O5N2SSi m/ e (M -
H) 541.2192, found 541.2192; 1H NMR (400 MHz, CDCl3) (â-
form) δ 0.11 (6H, s, TBDMS Si-Me), 0.93 (9H, s, TBDMS Si-
tBu), 1.25 (3H, s, isopropylidene-CH3), 1.37 (3H, s, isopropylidene-
CH3), 1.72 (1H, bs, NH), 3.11 (1H, ddd, 4-H, J 3,4 ) 4.4 Hz, J 4,5a
) 6.9 Hz, J 4,5b ) 5.5 Hz), 3.86 (1H, dd, 5-Ha, J 4,5a ) 6.9 Hz, J gem
) 9.9 Hz), 3.97 (1H, dd, 5-Hb, J 4,5b ) 5.5 Hz, J gem ) 9.9 Hz),
4.63 (1H, d, 1-H, J 1,2 ) 4.4 Hz), 4.71 (1H, dd, 2-H, J 1,2 ) 4.4 Hz,
J 2,3 ) 5.9 Hz), 5.08 (1H, dd, 3-H, J 2,3 ) 5.9 Hz, J 3,4 ) 4.4 Hz),
6.84-8.03 (10H, m, PhH, indole). Anal. Calcd for C28H37O5N2-
SSi: C, 62.07; H, 6.89; N, 5.17. Found: C, 62.23; H, 6.73; N,
5.34.
5-O-(ter t-Bu tyld im eth ylsilyl)-2,3-O-isop r op ylid en e-1-[2-
[N-(p h en ylsu lfon yl)in d olyl]]-D-r ibitol (6c): foam; IR (KBr)
870, 1090, 1200, 1400, 1470, 2900, 3400 cm-1; HRMS (FAB, NBA
+ KI) calcd for C28H39O7NSSiK m/ e (M + K) 600.1854, found
600.1854; 1H NMR (270 MHz, CDCl3): (R-for m ) δ 0.11 (6H, s,
TBDMS Si-Me), 0.93 (9H, s, TBDMS Si-tBu), 1.37 (3H, s,
isopropylidene-CH3), 1.53 (3H, s, isopropylidene-CH3), 2.85 (1H,
bs, 1 or 4-OH), 3.29 (1H, bs, 1 or 4-OH), 3.68-4.71 (5H, m, 2-H,
3-H, 4-H, 5-Ha, 5-Hb), 5.98 (1H, m, 1-H), 6.83 (1H, s, indole 3′-
H), 7.18-8.16 (9H, m, Ph-H, indole 4′-H, 5′-H, 6′-H, 7′-H); (S-
for m ) δ 0.13 (6H, s, TBDMS Si-Me), 0.94 (9H, s, TBDMS Si-
tBu), 1.31 (3H, s, isopropylidene-CH3), 1.38 (3H, s, isopropylidene-
CH3), 3.54 (1H, bs, 1 or 4-OH), 3.68-4.71 (5H, m, 2-H, 3-H, 4-H,
5-Ha, 5-Hb), 4.79 (1H, bs, 1 or 4-OH), 5.80 (1H, m, 1-H), 6.82
(1H, s, indole 3′-H), 7.18-8.16 (9H, m, Ph-H, indole 4′-H, 5′-H,
6′-H, 7′-H). Anal. Calcd for C28H39O7NSSi: C, 59.86; H, 7.00;
N, 2.49. Found: C, 59.93; H, 7.09; N, 2.65.
Oxid a t ion of 6 To Give Ar yl Dik et on es 7. Typ ica l
P r oced u r e. A solution of TFAA (5 mmol) in CH2Cl2 (1 mL)
was added dropwise to a solution of DMSO (5 mmol) in CH2Cl2
(5 mL) at -78 °C and stirred for 1 h at the same temperature.
To the stirring mixture was added dropwise a solution of 6 (1
mmol) in CH2Cl2 (3 mL) at -78 °C, and then the reaction
mixture was stirred for an additional 2 h at the same temper-
ature. A solution of Et3N (8 mmol) in CH2Cl2 (2 mL) was added
dropwise, and the stirring was continued for 0.5 h at -78 °C.
The reaction mixture was removed from the cooling bath and
allowed to warm to 0 °C with stirring. The reaction mixture
was partitioned between CH2Cl2 and ice-water. The organic
layer was separated, washed with 2 N HCl and saturated
aqueous NaHCO3, and dried over Na2SO4. The solvent was
removed, and the residue was purified by column chromatog-
raphy (AcOEt/hexane, 1/3) to give 7.
(2R ,3S )-5-O -(t er t -B u t y ld im e t h y ls ily l)-2,3-O -is o p r o -
p ylid en e-1-(2-th ien yl)-1,4-p en ta n ed ion e (7a ): oil; IR (neat)
840, 1100, 1240, 1400, 1650, 1720, 2900 cm-1; HRMS (FAB,
NBA) calcd for C18H29O5SSi m/ e (M + H) 385.1505, found
1
385.1505; H NMR (400 MHz, CDCl3) δ -0.01 (3H, s, TBDMS
Si-Me), 0.06 (3H, s, TBDMS Si-Me), 0.85 (9H, s, TBDMS Si-
tBu), 1.46 (3H, s, isopropylidene-CH3), 1.48 (3H, s, isopropyl-
idene-CH3), 4.34 (1H, d, 5-Ha, J gem ) 17.5 Hz), 4.53 (1H, d, 5-Hb,
J gem ) 17.5 Hz), 4.92 (1H, d, 3-H, J 2,3 ) 6.6 Hz), 5.57 (1H, d,
2-H, J 2,3 ) 6.6 Hz), 7.16 (1H, m, thiophene 4′-H), 7.71 (1H, m,
thiophene 3′-H), 7.98 (1H, m, thiophene 5′-H). Anal. Calcd for
C18H29O5SSi: C, 56.07; H, 7.58. Found: C, 55.98; H, 7.42.
Dep r otection of 8 To Give C-Aza n u cleosid e 9. Typ ica l
P r oced u r e. Compound 8 (0.5 mmol) was dissolved in aqueous
CF3CO2H (5 mL, 70% v/v) and stirred at 50 °C for 2 h. The
mixture was concentrated, and the residue was purified by pTLC
(CHCl3/MeOH, 9/1) to give 9.
(2R,3S)-1-(2-Ben zofu r yl)-5-O-(ter t-b u t yld im et h ylsilyl)-
2,3-O-isop r op ylid en e-1,4-p en ta n ed ion e (7b): oil; IR (neat)
870, 1270, 1550, 1690, 1740, 2900 cm-1; HRMS (FAB, NBA)
calcd for C22H31O6Si m/ e (M + H) 419.1890, found 419.1883;
1H NMR (270 MHz, CDCl3) δ -0.01(3H, s, TBDMS Si-Me), 0.07
(3H, s, TBDMS Si-Me), 0.86 (9H, s, TBDMS Si-tBu), 1.51 (6H,
s, isopropylidene-CH3), 4.41 (1H, d, 5-Ha, J gem ) 17.8 Hz), 4.57
(1H, d, 5-Hb, J gem ) 17.8 Hz), 5.02 (1H, d, 3-H, J 2,3 ) 6.7 Hz),
5.67 (1H, d, 2-H, J 2,3 ) 6.7 Hz), 7.31-7.80 (1H, m, benzofuran).
Anal. Calcd for C22H31O6Si: C, 62.98; H, 7.45. Found: C, 62.95;
H, 7.60.
1,4-Did eoxy-1,4-im in o-1-(2-th ien yl)-D-r ibitol (9a ): oil; IR
(neat) 800, 1020, 1200, 1420, 1660, 3300 cm-1; HRMS (FAB,
NBA + NaCl) calcd for C9H13O3NSNa m/ e (M + Na) 238.0514,
found 238.0521; 1H NMR (270 MHz, CD3OD) (â-form) δ 3.75 (1H,
m, 4-H), 3.88-3.91 (2H, m, 5-Ha, 5-Hb), 4.31 (1H, dd, 2-H, J 1.2
) 3.6 Hz, J 2,3 ) 4.3 Hz), 4.58 (1H, dd, 3-H, J 2,3 ) 4.3 Hz, J 3,4
)
7.7 Hz), 4.81 (1H, d, 1-H, J 1,2 ) 3.6 Hz), 7.06 (1H, m, thiophene
4′-H), 7.33 (1H, m, thiophene 3′-H), 7.49 (1H, m, thiophene 5′-
H). Anal. Calcd for C9H13O3NS: C, 50.21; H, 6.09; N, 6.51.
Found: C, 50.40; H, 6.13; N, 6.35.
(2R ,3S )-5-O -(t er t -B u t y ld im e t h y ls ily l)-2,3-O -is o p r o -
p ylid en e-1-[2-[N-(p h en ylsu lfon yl)in d olyl]]-1,4-p en ta n ed i-
on e (7c): foam; IR (KBr) 830, 1180, 1250, 1370, 1420, 1680,
1720, 2900 cm-1; HRMS (FAB, NBA + KI) calcd for C28H35O7-
NSSiK m/ e (M + K) 596.1541, found 596.1534; 1H NMR (270
MHz, CDCl3) δ 0.05 (3H, s, TBDMS Si-Me), 0.08 (3H, s, TBDMS
Si-Me), 0.90 (9H, s, TBDMS Si-tBu), 1.34 (3H, s, isopropylidene-
CH3), 1.44 (3H, s, isopropylidene-CH3), 4.37 (1H, d, 5-Ha, J gem
) 17.8 Hz), 4.55 (1H, d, 5-Hb, J gem ) 17.8 Hz), 5.03 (1H, d, 3-H,
J 2,3 ) 6.6 Hz), 5.71 (1H, d, 2-H, J 2,3 ) 6.6 Hz), 7.24-8.11 (10H,
m, PhH, indole). Anal. Calcd for C28H35O7NSSi: C, 60.30; H,
6.33; N, 2.51. Found: C, 60.45; H, 6.50; N, 2.55.
1-(2-Ben zofu r yl)-1,4-dideoxy-1,4-im in o-D-r ibitol (9b): solid;
IR (KBr) 800, 1140, 1200, 1670, 3400 cm-1; HRMS (FAB, NBA
+ NaCl) calcd for C13H15O4NNa m/ e (M + Na) 272.0899, found
1
272.0894; H NMR (270 MHz, CD3OD) (â-form) δ 3.41 (1H, m,
4-H), 3.76-3.85 (2H, m, 5-Ha, 5-Hb), 4.35-4.36 (2H, m, 2-H,
3-H), 4.53 (1H, m, 1-H), 6.86 (1H, s, benzofuran 3′-H), 7.16-
7.27 (2H, m, benzofuran 5′-H, 6′-H), 7.43-7.56 (2H, m, benzo-
furan 4′-H, 7′-H). Anal. Calcd for C13H15O4N: C, 62.64; H, 6.07;
N, 5.62. Found: C, 62.53; H, 6.11; N, 5.58.