EFFECT OF THE 7-METHYL SUBSTITUENT ON THE RING-OPENING PROCESS OF THE DIASTEREOISOMERIC BENZYLIC EPOXIDES DERIVED FROM 1,2,3,9,10,10A-HEXAHYDROPHENANTHRENE - DIFFERENCES AND SIMILARITIES BETWEEN DIFFERENT 2-ARYLOXIRANE MODELS

The introduction of an electron-donating substituent (7-Me group) on the 1,2,3,9,10,10a-hexahydrophenanthrene system, influences differently the diastereoselectivity of the acid hydrolysis of the diastereoisomeric couples of benzylic epoxides 3a and 4a and 3b and 4b. While in 3b-4b an increase of the syn diastereoselectivity is observed, in 3a-4a a complete anti diastereoselectivity is found. On the other hand, the trichloroacetolyses of both 4a and 4b yield rearrangement products only, contrary to the unsubstituted derivatives 3a and 3b where consistent amounts of addition products were observed. The results obtained underline that system 3 presents apparent chemical similarities with system 2 and differs from 1 to which it is more closely related.