1,3-Dioxanone Derivatives from β-Hydroxy-carboxylic Acids and Pivalaldehyde. Versatile Building Blocks for Syntheses of Enantiomerically Pure Compounds. A Chiral Acetoacetic Acid Derivative Preliminary Communication |
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Authors: | Dieter Seebach Jürg Zimmermann |
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Abstract: | (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 stereogenic center of the starting β-hydroxy acid without racemization and without using a chiral auxiliary. |
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