Enaminone‐Based Synthesis of Dipodazine Derivatives

Abstract

Abstract A series of racemic dipodazine analogues 9 were prepared in 22–80% yield from (3 Z ,6 RS )‐3‐[(dimethylamino)methylidene]‐6‐methyl‐1‐(phenylmethyl)piperazine‐2,5‐dione ( 7 ) ( Scheme 1 ), which was prepared in four steps from ( RS )‐alanine methyl ester hydrochloride. The preparation of nonracemic 7 from ( S )‐alanine methyl ester hydrochloride failed, since the introduction of the enamino functionality at position 3 of the precursor 6 was accompanied by almost complete racemization.