Pictet–Spengler reaction: is carbonyl the best choice? A highly diastereoselective alternative approach to trans-1,3-disubstituted tetrahydro-β-carbolines

Unprecedented 1,2,3-trisubstituted tetrahydro-β-carbolines (THBCs) have been synthesized via a short and highly diastereoselective synthetic route. The key step of the sequence is a flexible variant of the Pictet–Spengler reaction employing synthetic equivalents of several non-available carbonyl compounds. Using one such synthon, the resultant THBC could be further ring-closed to a tetracyclic indole alkaloidal skeleton.