Enantioselective synthesis of new oxazolidinylthiazolidines as enzyme inhibitors

A new procedure for thioester deprotection using thioglycolic acid in both homogeneous and heterogeneous phase

Classic acetyl thioester protection/deprotection methodologies are widely used in organic synthesis, but deprotection step usually requires harsh conditions not suitable for labile substrates. In this work, a new method for thioester deprotection using a thiotransesterification approach is described. Firstly, thioglycolic acid (TGA) was identified as a good deprotecting reagent in solution. In order to develop a thiol polymer-supported reagent, TGA was anchored to a PEG-based resin through an amide bond (TG-NCO-SH). Both homogeneous and heterogeneous approaches were conveniently carried out at room temperature, in aqueous buffer at pH 8. The mild conditions were suitable for alkyl and phenyl thioesters. Moreover labile thioesters containing thiazolidine and oxazolidine scaffolds, bearing amine, ester and acetal functionalities were also deprotected. The polymer-supported TGA gave better deprotection yields compared to TGA in solution, yields ranging from 61 to 90%. The feasibility of the recovery and reuse of TG-NCO-SH reagent was explored, showing it can be reused at least five times without lossing the activity.

Synthesis of bicyclic 1,4-thiazepines as novel anti-Trypanosoma brucei brucei agents

1,4-Thiazepines derivatives are pharmacologically important heterocycles with different applications in medicinal chemistry. In the present work, we describe the preparation of new bicyclic thiazolidinyl-1,4-thiazepines 3 by reaction between azadithiane compounds and Michael acceptors. The reaction scope was explored and the yields were optimized. The activity of the new compounds was evaluated against Nippostrongylus brasiliensis and Caenorhabditis elegans as anthelmintic models and Trypanosoma brucei brucei. The most active compound was 3l, showing an EC₅₀ = 2.8 ± 0.7 μM against T. b. brucei and a selectivity index >71.