The fragmentation patterns of nine di-, tri- and tetracyclic hydroquinones with potential antitumor activity were rationalized by invoking competing mechanisms that included sterically accelerated homolytic cleavage, Meerwein-type rearrangements and dehydrations through elimination or intramolecular nucleophilic substitution.

The synthesis of five new tetracyclic benzopsoralen analogues, compounds 2-6, with 9H-xanthen-9-one or 9H-carbazole frameworks, is described. Their inhibitory effects on the growth of three human tumor cell lines (MCF-7, SF-268, and NCI-460) were evaluated, and discussed in terms of structure-activity relationship, taking into account both geometric and electronic features. Generally, the angul...

A copolymer donor PBDTTPTP based on a tetracyclic bislactone unit, thieno[2',3':5,6]pyrano[3,4-d]thieno[3,2-b]pyran-4,9-dione (TPTP), was developed. The single crystal structure of TPTP derivative indicates the π-extended planar geometry and...

Tetracyclines are aromatic polyketides biosynthesized by bacterial type II polyketide synthases. The amidated tetracycline backbone is biosynthesized by the minimal polyketide synthases and an amidotransferase homologue OxyD. Biosynthesis of the key intermediate 6-methylpretetramid requires two early tailoring steps, which are cyclization of the linearly fused tetracyclic scaffold and regiosele...

The Rh(II)- and Cu(II)-catalyzed reactions of N-bis(trimethylsilyl)methyl, N-(2-indolyl)methyl α-diazoamides are investigated to delineate how conformational, steric and electronic factors influence the site- and chemoselectivity of the metallocarbenoid reaction. The N-bis(trimethylsilyl)methyl (N-BTMSM) group is found to be essential in promoting the metallocarbenoid reaction at the N-(2-indol...