- Claisen Orthoester Rearrangement in the Direct Preparation of Z-Isositsirikine and Z-Geissoschizine Derivatives Possessing the Right Oxidation State at C-17
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The Claisen orthoester rearrangement utilizing allylic alcohol 1 (or 2) and trimethyl 3-methoxyorthopropionate 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 , the intermediate ketene acetals 25a,b do not rearrange according to the Claisen mechanism to form compounds 26a,b and/or possessing two 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.
- Lounasmaa, Mauri,Hanhinen, Pirjo,Jokela, Reija
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p. 8623 - 8648
(2007/10/02)
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