Some synthetic uses of amino acids and studies towards the synthesis of germacrene A

Saunders, Gavin Nicholas (1980) Some synthetic uses of amino acids and studies towards the synthesis of germacrene A. University of Southampton, Doctoral Thesis.

Abstract

The synthesis of amino acids by the alkylation of arylideneamino esters was investigated. Imine derivatives of glycine and phenylalanine esters were prepared using benzaldehyde, 2-nitrobenzal.dehyde, 4-nitrobenzaldehyde, pyridine-4-aldehyde, 4-chlorobenzaldehyde, and 2,4-dichlorobenzaldehyde. In contrast to the other derivatives 2,4-dichlorobenzylidene phenylalanine methyl ester and 2,4-dichlorobenzylidene glycine ethyl ester were found to be stable, crystalline compounds. A variety of alkylation reactions were carried out on the 2,4-dichlorobenzylidene derivatives, using strong base at low temperatures. A method for the facile phase-transfer alkylation of these compounds has also been developed. In addition, acylation of 2,4-dichlorobcnzylidene glycine methyl ester has been achieved at low temperature in the presence of strong base, and the conversion of the resultant compounds to 3-oxo-2aminR ester hydrochlorides has been demonstrated. In part two the attempted synthesis of the ten-membered ring triene germacrene A, and related studies, is described. The planned synthesis involved a palladium (0) catalyzed intramolecular coupling of an allylic acetate precursor methyl 2-adetyl-11-acetyloxy-5,9-dimethylundeca-5,9-dienoate. This was prepared by a route beginning with geranyl acetate. Attempted cyclization led only to elimination of the acetate group. The analogous six-membered ring precursor was prepared by conventional methods. Attempted cyclilzation of this compound led to dihydropyran derivatives from 0-alkylation of the intermediate enolate.

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