Glaxo Group Limited

Roger Dansey

Alexander W Oxford

Frank Ellis

David Hartley

Compounds of the formula (I) ##STR1## (in which X represents HS-- or a group R.sub.1 R.sub.2 N-- wherein R.sub.1 and R.sub.2 which may be the same or different represent hydrogen or a straight or branched chain alkyl group containing from 1 to 4 carbon atoms or a benzyl group and R.sub.3 represents a C.sub.3-7 alkyl group or a C.sub.3-7 cycloalkyl group) are prepared by reacting an .alpha.-ketoester of the formula (II) ##STR2## (in which Alk represents an alkyl group) or a precursor thereof with a compound of the formula (III) ##STR3## The precursor of the compound of formula (II) may be a mixture of isomeric enol esters ##STR4## The compounds of formula (I) may be converted into compounds of formula VIII ##STR5## in which R.sub.1 and R.sub.2 which may be the same or different represent hydrogen or a straight or branched chain alkyl group containing from 1 to 4 carbon atoms, and R.sub.3 is as defined above.

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Welwyn, United Kingdom

Roger Dansey