Herein we demonstrate a chemoselective reaction of Nβ‐protected amino alkyl sulfonyl azides with in situ generated Nα‐protected amino acid selenocarboxylates via step wise intramolecular cyclization followed by decomposition to obtain N‐acyl sulfonamide tethered peptidyl conjugates. The protocol offers the synthesis of orthogonally protected N‐acyl sulfonamide tethered peptidomimetics under simple and mild reaction conditions employing commercially available amino acids in presence of NaBH2Se3 as a selenating agent. Also, the synthesis of N‐acyl sulfonamide tethered amino acid and aryl conjugates were accomplished as an extension of the above strategy.

The cis-amide bond isostere, 1,5-disubstituted tetrazole,has been introduced in the peptideb ackbone by as imple route startingf rom the thiopeptide. The desired 1,5-disubstituted tetrazole peptidomimetics were synthesized by the desulfurization of thiopeptides by using HgCl 2 in the presence of NaN 3 /TEA in DMF in good yields. Various other thiophilic reagents including hypervalent iodine reagents failed to deliver the tetrazole product with the exception of CBr 4 /PPh 3 ,w hich resulted in moderate yields. The advantage of the presentp rotocol over previousm ethods has been demonstrated by the selective insertion of tetrazole into peptide-thiopeptide hybrids. Also, the protocol is compatible with commonly employed urethane protecting groups (Fmoc, Boc, and Cbz) in peptidec hemistry.T hiopeptide Boc-Pro-y[CSNH]-Val-OMe (2i)a nd two tetrazole pepti-domimeticsC bz-Ala-y[CN 4 ]-Phe-OMe( 3d)a nd Boc-Proy[CN 4 ]-Val-OMe( 3i)w ere obtained as single crystalsa nd their molecular structures have been confirmed by X-ray crystallography.

Protic solvents furnished amino phosphinodiselenoic acid esters, whereas β-amino diselenides were obtained exclusively when reactions performed in polar aprotic solvents.

Chiral amino acid-derived formamides represent one of the most versatile components in multicomponent reactions. Herein, we describe a facile synthesis of N β -protected amino sulfenyl methyl formamides and sulfonyl methyl formamides via the Mannich reaction of N α -protected amino alkyl thiols followed by oxidation using 3-chloroperbenzoic acid (m-CPBA). This protocol is applicable to a wide range of Fmoc-and Cbz-protected amino acids. Notably, the reaction provides high yield and retains the stereochemistry of the chiral center of the starting component.

The title transformation is successfully performed starting from various thiodipeptides as well as amide‐thioamide hybride peptides, leaving the amide moiety intact.