We report the development of routes for the synthesis of three types of polycyclic indolic compounds, all possessing a tetrahydro-beta-carboline sub-structure to which an additional 5 or 6-membered heterocycle is attached across the 1,2-positions of ring C; ail three routes involve a Pictet-Spengler reaction as a key step, which can be used to control the stereochemistry of up to 5 chiral centres. (C) 1999 Elsevier Science Ltd. All rights reserved.
We report the development of routes for the synthesis of three types of polycyclic indolic compounds, all possessing a tetrahydro-beta-carboline sub-structure to which an additional 5 or 6-membered heterocycle is attached across the 1,2-positions of ring C; ail three routes involve a Pictet-Spengler reaction as a key step, which can be used to control the stereochemistry of up to 5 chiral centres. (C) 1999 Elsevier Science Ltd. All rights reserved.
A mild and efficient protocol for the Pictet-Spengler reaction in water using an acid catalyst has been described. The condensation of tryptophan, tryptamine, and N-b-benzyl tryptophan with different aldehydes having both electron-withdrawing and -donating substituents in the presence of a catalytic amount of TFA in water furnished tetrahydro-beta-carbolines in good isolated yields. A salient feature of the water mediated Pictet-Spengler reaction was the general trend observed during the condensation of Trp-OMe and aryl/aliphatic aldehydes furnishing diastereomeric mixtures with a preference for the cis-isomer. (c) 2007 Elsevier Ltd. All rights reserved.