(α-Alkylation of α-heterosubstituted carboxylic acids without racemization
作者:Dieter Seebach、Reto Naef、Giorgio Calderari
DOI:10.1016/s0040-4020(01)82417-0
日期:1984.1
α-Hydroxy- and α-mercapto-carboxylic acids are condensed with pivalaldehyde to give 2-t-butyl-5-substituted-l,3-dioxolanones or 1,3-oxathiolanones (2); the predominate CK-isomers are separated by crystallization. The cis-disubstituted heterocycles 2 derived from lactic, mandelic and malic acid furnish, after deprotonation with LDA, reaction with electrophiles such as alkyl halides, aldehydes and ketones
Enantioselective Generation and Diastereoselective Reactions of Chiral Enolates Derived from ?-Heterosubstituted Carboxylic Acids. Preliminary Communication
作者:Dieter Seebach、Reto Naef
DOI:10.1002/hlca.19810640829
日期:1981.12.16
Dioxolanones 7 and 8a and oxazolinones 9a derivedfrom pivalaldehyde and lactic acid, mandelic acid, and proline, respectively, furnish chiral enolates of type 3 by deprotonation with LDA. Reactions of these enolates with alkyl halides, aldehydes, and ketones ( 8b, 9b, 11–13) are highly diastereoselective. Thus, the overall enantioselective α-alkylation of chiral, non-racemic α-heterosubstituted carboxylic
Studies in stereoselective [2+2]-cycloadditions with dichloroketene
作者:David I. MaGee、Tammy C. Mallais、Peter D.M. Mayo、George M. Strunz
DOI:10.1016/j.tet.2006.02.014
日期:2006.4
During the investigation of the reaction of dichloroketene with cyclic enoxy-lactones and acyclic enoxy-ester substrates it was found that only the acylic variants effectively participated in the [2+2]-cycloaddition. Although a complete understanding of the reasons for this are lacking, molecular mechanics calculations do suggest that an out of plane twist of the cabonyl group in the acyclic compounds
Total Synthesis and Determination of the Absolute Configuration of Parimycin
作者:Day-Shin Hsu、Jiun-Yi Huang
DOI:10.1021/acs.orglett.9b02999
日期:2019.9.20
synthetic steps. Intermolecular Diels–Alder reaction of 6 with diene 7, cyclodehydrogenation catalyzed by iodine-dimethyl sulfoxide, and sodium dithionite reduction were the key steps. The absoluteconfiguration of natural parimycin was determined to be S.
A new highly diastereoselective synthesis of 2,5-disubstituted-1,3-dioxolan-4-ones from α-hydroxyacids
作者:N. Chapel、A. Greiner、J-Y. Ortholand
DOI:10.1016/0040-4039(91)80352-7
日期:1991.3
Reaction of α-hydroxyacids with acetals under weak acid catalysis gave the corresponding dioxolanones with a better diastereomeric ratio than the usual strong acid catalyzed synthesisfrom aldehydes.