Khaled Q. Shawakfeh

Synthesis of bis-diosgenin pyrazine dimers: new cephalostatin analogs.

A convenient synthesis for bis-diosgenin pyrazine dimers, cephalostatin analogues is reported. These symmetrical dimeric steroid-pyrazines were obtained by the classical condensation of alpha-amino ketones, the most efficient method for pyrazine ring construction.

Cyclization of free radicals at the C-7 position of ethyl indole-2-carboxylate derivatives: an entry to a new class of Duocarmycin Analogues.

Aryl free-radicals generated at the C-7 position of ethyl indole-2-carboxylates bearing N-allyl and propargylic groups triggered intramolecular cyclizations to furnish a new class of Duocarmycin analogues, formal ethyl pyrrolo[3,2,1-ij]quinoline-2-carboxylate derivatives, through the less favorable 6-endo-trig cyclization mode.

Synthesis of new symmetrical bis-steroidal pyrazine analogues from diosgenin

New symmetrical bis-steroidal pyrazine dimers that are cephalostatins/ritterazines analogues have been prepared easily from a cheap, readily available natural steroid (diosgenin). These dimers were obtained by classical, condensation of α-amino ketones in order to construct the pyrazine rings. The three dimers differ in the functionalized diosgenin: (25R)-5α,6β-dihydroxy-5α-spirosta-3-one, (25R)-4,5α-epoxy-5β-spirosta-3,6-dione and (25R)-5α-hydroxy-5α-spirosta-3,6-dione respectively.