G. Nagendra

Chiral N-Fmoc-β-Amino Alkyl Isonitriles Derived from Amino Acids: First Synthesis and Application in 1-Substituted Tetrazole Synthesis

A novel class of optically active N-Fmoc-protected amino isonitriles has been described for the first time. Conversion of the carboxyl group of Fmoc-beta-amino acids into an isocyano group has resulted in a new class of N-urethane-protected amino isonitriles. All the isonitriles have been isolated as stable solids, purified, and completely characterized. A synthetic application of the obtained isonitriles has also been demonstrated through the synthesis of 1-substituted tetrazole analogues of amino acids via a 2 + 3 cycloaddition with trimethylsilyl azide.

Synthesis of Boc‐Amino Tetrazoles Derived from α‐Amino Acids

Abstract A simple route for the synthesis of Boc-protected tetrazole analogs of amino acids starting from N α-Boc amino acids has been described. The [2 + 3] cycloaddition of Boc-α-amino nitrile and sodium azide in the presence of a catalytic amount of zinc bromide yielded the desired tetrazoles in good yields and purity. All the compounds obtained have been characterized by 1H and 13C-NMR and mass spectral studies.

Ultrasound accelerated conversion of Nα-urethane protected peptide esters to their thiopeptides using P2S5

A fast and efficient synthesis of N(alpha)-protected thiopeptide esters from the corresponding peptide esters using P(2)S(5) as thionating agent assisted by ultrasonication has been described. The conversion of peptide bond into thioamide was complete in 20-40 min at rt. The reaction was accomplished without using any base. The products isolated were characterized using (1)H NMR, (13)C NMR and mass spectroscopy.

Total Synthesis of Cyclosporin O: Exploring the Utility of Bsmoc-NMe- Amino Acid Fluorides and KOAt

Cyclosporin O (CyO), an immunosuppressent cyclic undecapeptide, was synthesized by convergent approach employing Bsmoc-Nmethyl amino acid fluorides and Potassium Salt of 7-Aza-1-hydroxybenzotriazole (KOAt) in solution by stepwise assembly. The couplings were found to be epimerisation free. The difficulty in the coupling of four consecutive N-methyl amino acids at position 8, 9, 10 and 11 was overcome by repeating the coupling thrice at these critical positions. All the ten protected peptide fragments of CyO starting from the dipeptide to the undecapeptide and final protected as well as CyO were isolated and fully characterized.