Synthesis of Antimicrobial Benzo[1,2,4]triazoloazepinium Salts and Tetrahydronaphtho[1,2-][1,2,4]triazines by Polar [3 + 2] and [4 + 2]-Cycloaddition Reactions.

Novel annulated azaheterocycles of benzo[1,2,4]triazoloazepine and tetrahydronaphtho[1,2-][1,2,4]triazine derivatives have been synthesized. Treatment of 2-diazenyl-1,2,3,4-tetrahydronaphthalen-2-yl acetates with BF·EtO generates 1-aza-2-azoniaallenium cation intermediates (or azocarbenium ions), which are intercepted by nitriles via cascade polar [3 + 2]-cycloaddition/rearrangement reactions to afford benzo[1,2,4]triazoloazepinium salts. These literature unprecedented fused tricycle compounds have been shown to exhibit antimicrobial activity against Gram-positive with in silico docking studies, suggesting that they may exhibit their antibiotic activity through inhibition of DNA gyrase.

Total Synthesis of Marine Alkaloids Motuporamines A and B via Ring Expansion of Cyclic β-Keto Esters.

An expedient total synthesis of the title marine sponge alkaloids has been developed. The salient features of the synthesis are as follows: (i) preparation of the required 13- and 14-membered cyclic lactams with + 4 ring-expansion strategy of cyclic β-keto esters and (ii) functional group manipulation of the resulted keto ester lactams. This approach used easily accessible and inexpensive materials/reagents, thus providing a promising alternative to the existing preparations.