M. Lounasmaa, P. Hanhinen, R. Jokela
Jul 31, 1995
Citations
0
Influential Citations
12
Citations
Journal
Tetrahedron
Abstract
Abstract The Claisen orthoester rearrangement utilizing allylic alcohol 1 (or 2 ) and trimethyl 3-methoxyortbopropionate 13a leads to Z-isositsirikine derivatives 21a–22a (or 23a–24a ) possessing one RO-function at C-17. In the cases of trialkyl 3,3-dialkoxyorthopropionates [triethyl 3,3-diethoxyorthopropionate 14b (or 3,3-diethoxymethylketene diethylacetal 20b ) and trimethyl 3,3-dimethoxyorthopropionate 14 a (or 3,3-dimethoxymethylketene dimethylacetal 20a )], the intermediate ketene acetals 25a,b do not rearrange according to the Claisen mechanism to form compounds 26a,b and/or 27a,b possessing two RO-functions at C-17. Syntheses of the intermediate orthoesters, trimethyl 3-methoxyorthopropionate 13a , trimethyl 3,3-dimethoxyorthopropionate 14a , trimethyl trans -3-methoxyorthoacrylate 20c , and triethyl 3,3-diethoxyorthopropionate 14b are described.