Sachitanand M. Mali

Copper(II) mediated facile and ultra fast peptide synthesis in methanol

A novel, ultrafast, mild and scalable amide bond formation strategy in methanol using simple thioacids and amines is described. The mechanism suggests that the coupling reactions are initially mediated by CuSO(4)·5H(2)O and subsequently catalyzed by in situ generated copper sulfide. The pure peptides were isolated in satisfactory yields in less than 5 minutes.

Thioacids mediated selective and mild N-acylation of amines.

N-Acylated amines are ubiquitous in nature. Selective N-acylation at neutral conditions remains a key area of interest. Here we are reporting the copper sulfate-mediated highly selective, mild, and rapid N-acylation of various aliphatic and aromatic amines using thioacids in methanol at neutral conditions. All N-acylated products of primary and secondary amines were isolated in good to excellent yields. This method is found to be highly selective for the amines and not sensitive to other functional groups such as phenols, alcohols, and thiols. The simple workup, high yields, and high selectivity of this reaction can be an attractive alternative to those of the existing acyl halide- and acid anhydride-mediated N-acylation reactions.

Synthesis and Structural Investigations of Functionalizable Hybrid β-Hairpin

The solution and solid state conformations of a designed β-hairpin containing functionalizable α,β-unsaturated γ-amino acids at the antiparallel β-strands and a single step transformation to its saturated γ-peptide analogue are studied.

Thioacetic Acid/NaSH-Mediated Synthesis of N-Protected Amino Thioacids and Their Utility in Peptide Synthesis

Thioacids are recently gaining momentum due to their versatile reactivity. The reactivity of thioacids has been widely explored in the selective amide/peptide bond formation. Thioacids are generally synthesized from the reaction between activated carboxylic acids such as acid chlorides, active esters, etc., and Na2S, H2S, or NaSH. We sought to investigate whether the versatile reactivity of the thioacids can be tuned for the conversion of carboxylic acids into corresponding thioacids in the presence of NaSH. Herein, we report that thioacetic acid- and NaSH-mediated synthesis of N-protected amino thioacids from the corresponding N-protected amino acids, oxidative dimerization of thioacids, crystal conformations of thioacid oxidative dimers, and the utility of thioacids and oxidative dimers in peptide synthesis. Our results suggest that peptides can be synthesized without using standard coupling agents.

Design of Stable β-Hairpin Mimetics through Backbone Disulfide Bonds

The synthesis and utilization of novel thiostatines (β-SH-substituted γ-amino acids) in the design of backbone-disulfide-stabilized β-hairpin mimetics, solution conformations of hybrid β-hairpins and Cys-disulfide-stabilized α-peptide analogue, their thiol exchange, and proteolytic stability are investigated. The results suggest that thiostatines can be used to design proteolytically stable water-soluble β-hairpin mimetics without deviating from overall β-hairpin conformation.