123. 1,3-Dioxanone Derivatives from β-Hydroxy-carboxylic Acids and Pivalaldehyde. Versatile Buiding Blocks for Syntheses of Enantiomerically Pure Compounds. A Chiral Acetoacetic Acid Derivative

Article abstract of DOI:10.1002/hlca.19860690523

(R)-3-Hydroxybutyric acid (from the biopolymer PHB) and pivalaldehyde give the crystalline cis- or (R,R)-2-(tert-butyl)-6-methyl-1,3-dioxan-4-one (1a), the enolate of which is stable at low temperature in THF solution and can be alkylated diastereoselectively (->3, 4, 5, and 7).Phenylselenation and subsequent elimination give an enantiomerically pure enol acetal 10 of aceto-acetic acid.Some reactions of 10 have been carried out, such as Michael addition (->11), alkylation on the CH3 substituent (->13), hydrogenation of the C=C bond (->1a) and photochemical cycloaddition (->16).The overall reactions are substitutions on the one sterogenic center of the starting β-hydroxy acid without racemization and without using a chiral auxiliary.