Chemoselective construction of novel steroid derivatives.
Alpha-halo-alpha-heteroarylalkyllithiums, generated by deprotonation of the corresponding halides, when added promptly to steroids with C=O or C=NR groups, lead to epoxides and aziridines. The reactions are regio- and stereoselective; in fact, in the presence of more than one C=O group, the oxido or aziridino functions are formed uniquely at the C=O of C-17 (or C-20 depending on its position in the starting molecule), and the C-20(R) stereoisomer is often the only product isolated. Protection of the hydroxyl group present on several considered steroids was required, and it was accomplished through derivatization in acetyl, ether, or lactone.
Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, University of Lecce, Via Prov.le Lecce, Monteroni, I- 73100 Lecce, Italy. luigino.troisi@unile.it
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D001388:Aziridines / Q000138:chemical synthesis / Q000737:chemistry; D004852:Epoxy Compounds / Q000138:chemical synthesis / Q000737:chemistry; D008094:Lithium / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D013237:Stereoisomerism; D013256:Steroids / Q000138:chemical synthesis* / Q000737:chemistry
D001388:Aziridines; D004852:Epoxy Compounds; D013256:Steroids; D008094:Lithium