CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

Based on this hypothesis, the alcohol 130 was oxidized with pyridinium chlorochromate
(PCC) in CH 2 Cl 2 to obtain the ketone 131, which was characterized from the IR peak at
1741 cm -1 , and also from the 13 C NMR resonance at δ 206.8 ppm. The 1 H and 13 C NMR
spectra of 131 are shown in Fig. IV.2.2 and Fig. IV.2.3 respectively. Reduction of 131
with NaBH 4 the alcohol 132 as a single stereomer. Alcohol 132 was characterized from the
IR hydroxyl peak at 3443 cm -1 , the 1 H NMR resonances at δ 4.92-4.99 (m, 2H) and at δ
5.61-5.75 (m, 1H) as well as the 13 C NMR peaks at δ 116.7 and 136.1 ppm due to the
olefin. The 13 C NMR spectrum established the diastereomeric purity of the compound 132.
69c
i
O
O
X
OTBDPS
iii
O
O
O
iv O
OR 1 OH OR 1 O
v
ii
128 X = CH 2
129 X = O
130 R 1 = TBDPS
131 R 1 = TBDPS
O
O
vi
O
O
vii
O
O
OR 1
OH
OH
OH
O
O
132 R 1 = TBDPS
132a
132b
(i) TBDPSCl, imidazole, CH 2 Cl 2 , 25 o C; (ii) O 3 , CH 2 Cl 2 , -78 o C; Ph 3 P; (iii) Allyl bromide,
Zn, THF, aqueous NH 4 Cl, 25 o C; (iv) PCC, NaOAc, CH 2 Cl 2 , 0 o C; (v) NaBH 4 , MeOH, 0
o C; (vi) Bu 4 NF, THF, 0 o C; (ii) DMP, PPTS, 25 o C.
Scheme IV.2.3
152