Synthesis and biological activity of a new class of insecticides: the N-(5-aryl-1,3,4-thiadiazol-2-yl)amides.

BACKGROUND: Optimization studies on a high-throughput screening (HTS) hit led to the discovery of a series of N-(6-arylpyridazin-3-yl)amides with insecticidal activity. It was hypothesized that the isosteric replacement of the pyridazine ring with a 1,3,4-thiadiazole ring could lead to more potent biological activity and/or a broader sap-feeding pest spectrum. The resulting N-(5-aryl-1,3,4-thiadiazol-2-yl)amides were explored as a new class of insecticides. RESULTS: Several methods for 2-amino-1,3,4-thiadiazole synthesis were used for the preparation of key synthetic intermediates. Subsequent coupling to variously substituted carboxylic acid building blocks furnished the final targets, which were tested for insecticidal activity against susceptible strains of Aphis gossypii (Glover) (cotton aphid), Myzus persicae (Sulzer) (green peach aphid) and Bemisia tabaci (Gennadius) (sweetpotato whitefly). CONCLUSION: Structure-activity relationship (SAR) studies on both the amide tail and the aryl A-ring of novel N-(5-aryl-1,3,4-thiadiazol-2-yl)amides led to a new class of insecticidal molecules active against sap-feeding insect pests. © 2016 Society of Chemical Industry.

Synthesis of antiproliferative Cephalotaxus esters and their evaluation against several human hematopoietic and solid tumor cell lines: uncovering differential susceptibilities to multidrug resistance.

Deoxyharringtonine (2), homoharringtonine (3), homodeoxyharringtonine (4), and anhydroharringtonine (5) are reported to be among the most potent members of the antileukemia alkaloids isolated from the Cephalotaxus genus. Convergent syntheses of these four natural products are described, each involving novel synthetic methods and strategies. These syntheses enabled evaluation of several advanced natural and non-natural compounds against an array of human hematopoietic and solid tumor cells. Potent cytotoxicity was observed in several cell lines previously not challenged with these alkaloids. Variations in the structure of the ester chain within this family of alkaloids confer differing activity profiles against vincristine-resistant HL-60/RV+, signalling new avenues for molecular design of these natural products to combat multi-drug resistance.

Strain-release rearrangement of N-vinyl-2-arylaziridines. Total synthesis of the anti-leukemia alkaloid (-)-deoxyharringtonine.

Deoxyharringtonine (1) is among the most potent of the anti-leukemia alkaloids isolated from the Cephalotaxus genus. A convergent total synthesis of (-)-1 is reported, involving novel synthetic methods and strategies that include (1) the strain-release rearrangement of N-aryl-2-vinylaziridines for [3]benzazepine synthesis, (2) a vinylogous amide acylation-cycloaddition cascade for spiro-pyrrolidine construction, and (3) efficient acylation of the cephalotaxine core by alpha-(beta-lactone)carboxylic acid derivatives to access the biologically active cephalotaxus esters. These innovations should allow rapid access not only to other Cephalotaxus alkaloids but also to non-natural analogues of potential therapeutic utility.