Mammalian Alkaloids: Configurations of Optically Active Salsoline‐ and 3′,4′‐Dideoxynorlaudanosoline‐1‐carboxylic Acids

Synthesis of the optical isomers of (±)‐methyl 6,7‐dimethyl‐3′,4′‐dideoxynorlaudanosoline‐1‐carboxylate ((±)‐ 2 ) was accomplished by reaction of (±)‐ 2 with (+)‐( R )‐1‐phenylethyl isocyanate, separation of the urea diastereoisomers (−)‐ 4A and (+)‐ 4B , and alcoholysis of the ureas in refluxing BuOH. Optically active isoquinoline‐carboxylates 2A , B and hydantoins 8A , B isolated were characterized. The absolute configuration of the reaction products was established by X‐ray analysis of the optically active hydantoin (+)‐ 8A . Hydrolysis of the methyl isoquinolinecarboxylates 2A , B with 48% HBr soln. at reflux afforded the desired optically active 3′,4′‐dideoxynorlaudanosoline‐1‐carboxylic acids 1A , B required for enzyme‐inhibition studies. Details of the X‐ray diffraction analysis of (+)‐methyl salsoline‐1‐carboxylate hydrobromide ((+)‐ 11A ·HBr) prepared earlier are included. CD spectra of (+)‐( S )‐methyl 6,7‐dimethyl‐3′,4′‐dideoxynorlaudanosoline‐1‐carboxylate hydrobromide ((+)‐ 2A . HBr) and (−)‐( R )‐methyl salsoline‐1‐carboxylate hydrochloride ((−)‐ 11B ·HCl) confirmed the assignment of their ( S )‐ and ( R )‐configurations, respectively.