A series of vinyl sulfone-containing peptidomimetics were rationally designed, synthesized, and evaluated against Trypanosoma brucei brucei . These electrophilic compounds are likely to exert their antitrypanosomal activity via inhibition of trypanosomal cysteine proteases, TbCatB and rhodesain, through alkylation of a key cysteine residue within the protease active site. The series was designed to present complementary groups to naturally recognized peptide substrates while probing tolerance to a range of substitutions at the P1, P1', and P2 positions. The most potent compound, 29 (EC50 = 70 nM, T. b. brucei whole cell assay), displayed minimal toxicity (>785 times selectivity) when assayed for cytotoxicity against the human promyelocytic leukemia (HL-60) cell line. Cells treated with compound 29, as with K777 (2), exhibited an increase in both the number of multinucleated cells and cells with swollen flagellar pockets. Computational analysis revealed a strong correlation between the hypothetical binding mode in TbCatB/rhodesain and trypanocidal activity in vitro.

Phosphate groups are often crucial to biological activity and interactions of oligonucleotides, but confer poor membrane permeability. In addition, the group's lability to enzymatic hydrolysis is an obstacle to its use in therapeutics and in biological tools. We present the synthesis of N ‐oxyamide and squaramide modifications at the 5’‐end of oligonucleotides as phosphate replacements and their biological evaluation using the 5’‐exonuclease SNM1A. The squaryl diamide modification showed minimal recognition as a 5’‐phosphate mimic; however, modest inhibition of SNM1A, postulated to occur through metal coordination at the active site, was observed. Their facile incorporation after solid‐phase synthesis and recognition by the exonuclease makes squaryl diamides attractive neutral 5’‐phosphate replacements for oligonucleotides. This work is the first example of squaryl diamide modifications at the 5’‐terminal position of oligonucleotides and of the potential use of modified oligonucleotides to bind to the metal center of SNM1A.

An operationally simple protocol for the synthesis of γ-hydroxy vinyl sulfones has been developed using a proline-based aldehyde aminooxylation, followed by a vinyl sulfone forming Horner-Wadsworth-Emmons olefination. The adducts, formed in high enantiopurity, were subsequently converted to γ-azido vinyl sulfones, and azide-alkyne click chemistry enabled the synthesis of vinyl sulfone-based triazoles as potential nonpeptidic cysteine protease inhibitors.

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An improved, Weinreb amide-based, synthesis of anti-trypanosomal lysine-containing vinyl sulfones is described incorporating, as a feature, diversity at the ε-lysine amino group. Members of this family demonstrated moderate to good efficacy as anti-trypanosomal agents and a fluorescent dansyl (19) derivative was used to investigate subcellular localisation of the compound class.