CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

N 3
O
Ph
Fig. IV.4.1. Structure of 2(S)-[1(S)-Azido-2phenylethyl]oxirane (VI)
IV.4.2: Previous syntheses
The first enantiospecific synthesis (Scheme IV.4.1) of the tile compound vI was
accomplished by Ghosh et al. 169d starting from optically pure and commercially available
diethyl D-tartarate 151. This was converted to benzylidene acetal 152. Reductive cleavage
of 152 by LiAlH 4
afforded the D-threitol derivative, which was converted to
isopropylidene derivative 153. Catalytic hydrogenation of 153 followed by treatment with
triphenylphosphine and diethyl azodicarboxylate yielded the epoxide 154, which was
treated with phenylmagnesium bromide to afford 155. Mitsonobu azidation and subsequent
deketalisation of 155 yielded 156, which was finally converted to the azido oxirane VI by
treatment with 2-acetoxy-isobutyryl chloride in chloroform followed by exposure of the
resulting chloroacetate derivative to sodium methoxide.
HO
HO
O
CO 2 Et
O
CO 2 Et
O
i
ii, iii
iv, v
Ph
O
HO
CO O
2 Et
CO 2 Et
OBn
O
151 152 153 154
O
vi
HO
O
O
vii, viii
N 3
OH
OH
ix, x
VI
Ph
155
Ph
156
169