Synthesis of a series of 3,4-methanoarginines as side-chain conformationally restricted analogues of arginine

A series of optically active stereoisomers of 3,4-methanoarginine (1-4 and ent-1-ent-4) with trans/cis, D/L, and syn/anti stereochemical diversity, the side-chains of which were restricted in various special arrangements, was designed as biologically useful arginine mimetics. These conformationally restricted arginine analogues were synthesized effectively by using a series of chiral 3,4-methanoamino acid equivalents (7-10 and ent-7-ent-10) as the key synthetic units. Their biological evaluation with three isoforms of nitric oxide synthase showed that trans-3,4-methano-L-syn-arginine (2) was a good substrate, having close potency to L-arginine, and isoforms selectivities were also similar to those of L-arginine. (C) 2011 Elsevier Ltd. All rights reserved.