ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Highly Diastereoselective α-Alkylation of β-Hydroxycarboxylic Acids Through Lithium Enolates of 1,3-Dioxan-4-onesFrom serine, β-hydroxyisobutyric acid (‘Roche’ acid) and β-hydroxybutyric acid, the dioxanones 1-6 were prepared. The generation of the enolates of type I with LDA at -75° and alkylation gave products with trans-configuration whereas protonation of the 5-methyl-substituted enolate allowed access to the cis-configurated β-hydroxybutyric-acid derivative 12. Hydrolysis gave the free β-hydroxy acids of ‘syn’-and ‘anti’-configuration. Alkylation of the 6-unsubstituted dioxanones 1 and 3 yielded predominantly products resulting from attack in the cis-position of the t-Bu group. The ‘reactive’ conformation of the enolates involved is tentatively derived from the product configuration. The selectivity of the alkylation is also discussed in terms of the results of an ab-initio calculation on the enolates M-P.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19880710527
