CHEM01200604012 Dibakar Goswami - Homi Bhabha National ...

appeaence of a sharp peak for the –Ots group at 1177 cm -1 in place of hydroxyl peak in the
IR spectrum. The 1 H NMR peak at δ 2.42 (3H) and at δ 4.66 (dd, J = 7.4 Hz and 2.2 Hz) [–
CH(OTs)] confirmed its formation. Subsequent hydrolysis of compound 105 with aqueous
TFA afforded the diol 106 (IR hydroxyl band at 3417 cm -1 and the absence of resonances
due to cyclohexylidene moiety in 1 H (Fig IV.1.2) and 13 C NMR (Fig. IV.1.3) spectra).
Next, copmpund 106 was dimesylated and the resultant trisulphonate was subjected to
LiAlH 4 reduction to produce the required C 3 H 7 unit directly. Unfortunately, this gave a
very poor yield of the desired product. Hence, an alternative strategy was employed. The
diol 106 was subjected to reductive detosylation with excess LiAlH 4 to give 107. The
formation of 107 was confirmed from the disappearance of the characteristic resonances
due to tosyl group in 1 H and 13 C NMR spectra. Dimesylation of hydroxyl groups of 107,
followed by LiAlH 4 reduction produced the alkene 109. Its 1 H NMR spectrum (Fig.
IV.1.4) showed a 6H triplet at δ 0.88 ppm for the two methyl groups. The 13 C NMR
spectrum (Fig IV.1.5) was also devoid of the peaks at δ ~60-70 ppm due to the oxygenated
carbons. Oxidative ozonolysis 116
of 109 under alkaline conditions, followed by base
catalysed hydrolysis of the resultant ester and subsequent acidification furnished the title
compound V in ~10% overall yield. The spectral and optical data of compound V were in
well conformity with the reported values. 143g
143