Veladi Panduranga

Amino acid fluorides: viable tools for synthesis of peptides, peptidomimetics and enantiopure heterocycles

This review provides a broad perspective of the uses of amino acid fluorides in the synthesis of peptides and a wide range of other molecules. The topic is discussed with reference to the preparation of N-protected amino acid fluorides, their reactivity, coupling and their synthetic applications. The merits of the use of amino acid fluorides as coupling agents for making difficult peptides and in combating the problem of stereomutation, as well as their successful use in solid phase peptide synthesis, are reported with examples. Recent developments in the application of amino acid fluorides for making amino acid derivatives, peptide conjugates, peptide mimics and heterocycles are also reviewed.

Synthesis of chiral Nβ-protected amino diselenides from the corresponding amino alkyl iodides using NaBH2Se3 as a selenating reagent and their conversion to seleninic acids

A convenient approach has been presented for the synthesis of Nβ-protected amino diselenides from the corresponding amino alkyl iodides using in situ generated NaBH2Se3 as an efficient selenating reagent. All the diselenides are obtained in good yields under very mild conditions, short duration times and the protocol is free from racemization. The methodology has been effectively extended to the synthesis of N-protected L-selenocystine methyl ester. Clean oxidation of Nβ-protected amino diselenides to Nβ-protected amino seleninic acids using 35% aqueous H2O2 has also been accomplished. The present protocol is compatible with all the common urethane protecting groups.

Oxidative Amidation of Benzyl Alcohols with Amino Acid Esters Mediated by N-hydroxysuccinimide/phenyliodine Diacetate

ABSTRACT A simple protocol involving metal-free oxidative amidation of benzyl alcohols with amino acid esters has been presented. The amidation proceeds in a radical pathway unlike in conventional metal-mediated extrusion of dihydrogen. The method is advantageous in terms of metal-free conditions, nonexpensive commercial starting substrates. Also various substituents in the starting materials are tolerated and sterically hindered amino acid side chains could provide good yields of amide products. GRAPHICAL ABSTRACT

Thionation of Di and Tripeptides Employing Thiourea as a Sulphur Transfer Reagent

A simple and efficient method for the synthesis of thiopeptides by the treatment of Nα-protected peptide esters employing DMF/PCl5 and thiourea as a sulphur transfer reagent is described. The conversion is carried out at room temperature within a short reaction time. The method is high yielding and free from racemization. Multiple thionation is demonstrated by conversion of two peptide bonds of tripeptides into thioamides. In addition, amino acid derived arylamides are also converted into aryl thioamides.