Abstract
The Pictet-Spengler reaction of Na-methyl-Nb-benzyltryptophan methyl ester hydrochloride (4a) with methyl 3-formylpropionate was carried out in 50% aqueous MeOH under reflux to afford methyl trans-2-benzyl-3-methoxycarbonyl-9-methyl-1, 2, 3, 4-tetrahydro-9H-pyrido [3, 4-b] indole-1-propionate (3a) as a major product and trans-2-benzyl-3-methoxycarbonyl-9-methyl-1, 2, 3, 4-tetrahydro-9H-pyrido [3, 4-b] indole-1-propionic acid (5a) as a minor product. In earlier work, the stereochemistry of the major product 3a had been erroneously assigned as 1, 3-cis (3b), while the minor product 5a had been incorrectly assigned as the 1, 3-trans compound 3a. Compound 3b was not formed in this reaction. The stereochemistry of the major product (3a) was confirmed by X-ray crystallographic analysis in the present work.
