Practical method for the synthesis of (R)-homopipecolinic acid and (R)-homoproline esters from ω-chloroalkanoic acids and available chiral amines
摘要:
A practical synthesis of (R)-homopipecolinic acid methyl ester 1 and (R)-homoproline methyl ester 2 was performed utilizing (i) a direct intramolecular cyclization of omega-chloro-beta-enamino esters 11 and 12, which were prepared from available (S)-1-phenylethylamine or (S)-1-(1-naphthyl)ethylamine and omega-chloro-beta-keto esters 5 and 10, respectively and (ii) a highly diastereoselective NaBH4 reduction followed by hydrogenolysis. The present method is a short-step process using inexpensive and readily available substrates and reagents with fewer wasted materials. (c) 2005 Elsevier Ltd. All rights reserved.