Exocyclic oxirane derivatives

A facile synthesis of 180 with a better yield has been developed as follows. O-Deacetylation of 51 with hydrochloric acid gave DL-(l,3/2)-3-bromomethyl-5-cyclo-hexene-1,2-diol (181). Stereospecific epoxidation of 181 with mCPBA and subsequent acetylation gave-the epoxide (182), which afforded the exocyclic methylene derivative (183) by dehydrobromination with silver fluoride [51]. Reductive cleavage of the oxirane ring of 183 with lithium aluminium hydride, followed by acetylation yielded... 

These compounds have a similar steric arrangement of the oxolane ring as do ordinary derivatives of furanoses. Exocyclic oxirane-ring closure proceeds readily as compared to endocyclic epoxides because the required trans-orientation of the reacting groups is adopted without significant steric hindrance. 

Acetalated myo-inositol derivatives have been converted by standard reactions into intermediates required for the total synthesis of sugarotoxin and some of its analogues, which are 6-0-acyl derivatives of myo-inositol.Quebrachitol reacts with DAST to a deoxy-fluoro derivative which, on demethylation, gave the fluoro-inositol (54), a cellular replication inhibitor.Deoxy-fluoro-myo-inositols have been prepared, and their behaviour as substrates for phosphatidyl-inositol synthetase has been reported. 2-C-fluoromethyl-myo-inositol (55) has been prepared conventionally from an exocyclic oxiran precursor. 

Oxidation of bicyclo[3.1.1]heptane derivatives containing an endocyclic double bond results selectively in the frans-oxirane 50 with respect to the geminal dimethyl bridge. The two diastereomers 51 and 52 are obtained from an exocyclic double bond. Menthenone yields exclusively C S-(+)-menthenone oxide 53, with known absolute configuration. ... 

Cob is the nonbonding MO (NBMO) coefficient on the carbon atom where the oxirane ring is opened. It is calculated according to the Longuet-Higgins zero sum rule for odd alternant aromatic hydrocarbons [36,65], Incidentally, the first authors to try such NBMO coefficients of exocyclic atoms of odd-alternant PAH derivatives were Dipple, Lawley and Brookes [66] in 1968. 

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