Lithium aluminum deuteride epoxides

The course of the ring opening in epoxides derived from various exocyclic methylene compounds by treatment with lithium aluminum deuteride has been studied in the norbornane series. ... 

Ascarylose (94) and the (35) deuterium-labeled ascarylose were prepared starting from methyl a-L-rhamnopyranoside via the 2,3-anhydro sugar 120 (Scheme 34).204 Opening of the epoxide ring with lithium aluminum hydride in THF led selectively to the 3-deoxy derivative. If reduction was performed with lithium aluminum deuteride, the methyl (3S)-[32H]ascaryloside (3S)-[32H]119 was obtained. 

Epoxides are excellent electrophiles and substrates for 5 2 reactions the release of strain in the three-membered ring makes them particularly reactive. They react with all the nucleophiles we have discussed, with reliable inversion of stereochemistry (Figure 9.74). Note that the stereochemistry in the products is relative, not absolute— since the starting material is not chiral, racemic mixtures would be obtained (hence, the plain rather than the tapered wedge and hash bonds). The one unfamiliar example here is the reaction with lithium aluminum deuteride, LilAlDJ. For the present, think of this as essentially a deuteride anion (or hydride from lithium aluminum hydride), but this reactive molecule will quickly become a good friend to you in reductions and devising syntheses. 

Reduction of an tt, -unsaturated epoxide. Reduction of 3iS-benzoyloxy-14a, 15a-epoxy-5a-cholest-7-ene (1) with lithium aluminum hydride (or deuteride) or... 

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