A convenient synthesis of conformationally constrained beta-substituted tryptophans

A short and general synthesis for the preparation of various conformational ly constrained beta-substituted tryptophans has been elaborated starting fr om indole, aldehydes and Meldrum's acid by using trimolecular condensation and Curtius rearrangement mediated functional group transformations followe d by deprotections, as key-steps. The relative configurations of the two di astereomeric series have been determined indirectly by the measurement of ( 3)J coupling constants in the corresponding tetrahydro-beta-carbolines, and further supported by means of molecular modelizations. (C) 2000 Elsevier S cience Ltd. All rights reserved.