Silyl protecting groups fert-butyldimethylsilyl

Whitesell and Minton have synthesized (- )-xylomollin (408), the only trans-fiised iridoid, from the racemic bicyclic diene 409. Control of the stereochemistry was effected in the first step by addition of the glyoxylate 410. The two products were separated and the major one, 411, was reduced with lithium aluminum hydride. Conversion of the primary alcohol to a methyl group, with concomitant inversion of stereochemistry at the secondary alcohol carbon atom was carried out by protection of the primary alcohol function (fert-butyldimethylsilyl), tosylation of the secondary hydroxyl, then removal of the silyl group with formation of an epoxide with inversion, and reduction (LiEtaBH) of the epoxide. The remaining steps are shown in Scheme 36. It remains to point out that isoxylomoUin (412) was produced preferentially, and is indeed formed from xylomollin (408) slowly in methanolic solution. ... 

AllylsUanes are reactive towards 1,3-dithienium tetrafluoroborate. The intermediate -silyl carbocation typically suffers elimination of the silyl cation to furnish a 2-allyl-1,3-dithiane (eq 5). This protocol was employed to homologate allylsilane 3 to produce dithiane 4, an intermediate in the synthesis of epiantillatoxin (eq 6). A fert-butyldimethylsilyl ether used as a protecting group was cleaved from 3 during this reaction. 

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