Theoretical Study Of Structural Features Of Endo, Exo Double Bonds And Side Chain In 14 Alpha-Demethylation Of Lanosterol

The 14 alpha-demethylation of biosynthetic reactions is carried out exclusively by lanosta-8,24-dien-3 beta-ol (lanosterol). Theoretical calculations were done to determine the importance of this structure with the Hartree-Fock scheme. It was modeled on structures similar to lanosterol with variations on the endo between C8-C9 (lanosta-7,24-dien-3 beta-ol and lanosta-6,24-dien-3 beta-ol) as compared with the exo between C24-C25 (Lanosta-8-en-3 beta-ol) and the size of the side chain (27-norlanosta-8-en-3 beta-ol, 26,27-dinorlanosta-8-en-3 beta-ol, 25,26,27-trinorlanosta-8-en-3 beta-ol, 24,25,26,27-tetranorlanosta-8-en-3 beta-ol, 23,24,25,26,27-pentanorlanosta-8-en-3 beta-ol, 22,23,24,25,26,27-hexanorlanosta-8-en-3 beta-ol). Energetic, electronic, and orbital evidence was found. The theoretical data were analyzed and were found to be important for the 14 alpha-demethylation, the presence of HOMO on the region C8-C9 and C14-14(1), a negative charge on the outgoing methyl C14(1). This atomic charge varies with the size of the side chain, and with the modification of the endo and exo double bonds. The conformation of the structure of the steroid is also related to its reactivity. (C) 2005 Wiley Periodicals, Inc.