G. Scherowsky, M. Sefkow
Aug 10, 1993
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0
Influential Citations
2
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Journal
ChemInform
Abstract
Optically active 3-hydroxybutyric and 3-hydroxyhexanoic acids were transformed into 3,4-disubstituted and 3,3,4-trisubstituted 2-oxetanones using two different approaches. Diastereoselecti ve alky lation was performed either on dioxanone enolates or on Iithoxy-lithium enolates. Some recently published unexpected results of alkylation of substituted dioxanones were used for the synthesis of a trisubstituted oxetanone. Results and Discussion Now we report on the synthesis of 3,4disubstituted and 3,3,4-trisubstituted 2oxetanones, which seemed us to be superior to 1 because of their larger lateral dipole moment and higher rigidity. The required optically active a-monoand adisubstituted 3-hydroxycarboxylic acids were synthesized in two different ways. (3S)-Ethyl 3-hydroxyhexanoate (3) was prepared by yeast reduction [7] of comercially available ethyl 3-oxohexanoate (2). (3R)-Hydroxybutyric acid (5) was obtained by depolymerization of poly(hydroxybutyric acid) (PRB, 4) with TsOR [8] (Scheme 1). The ethyl ester 3 was alkylated with the benzylic bromide 7 [9] with high diastereoselectivity via the lithoxy-lithium