Photooxygenation of pregnanes
The course of the singlet-oxygen reaction with pregn-17(20)-enes and pregn-5,17(20)-dienes was studied to compare the reactivity of the two alkene moieties present in some steroid families. Thus, from commercially available (3β,5α)-hydroxy-androstan-17-one and (3β)-3-hydroxyandroxst-5- en-17-one, th...
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2004
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0018019X_v87_n12_p2987_Ponce http://hdl.handle.net/20.500.12110/paper_0018019X_v87_n12_p2987_Ponce |
| Aporte de: |
| Sumario: | The course of the singlet-oxygen reaction with pregn-17(20)-enes and pregn-5,17(20)-dienes was studied to compare the reactivity of the two alkene moieties present in some steroid families. Thus, from commercially available (3β,5α)-hydroxy-androstan-17-one and (3β)-3-hydroxyandroxst-5- en-17-one, the following 3-{[(tertbutyl)dimethylsilyl]oxy}-substituted, 17(20)-unsaturated pregnanes were prepared (see Fig. 1): (3β,5α)-21- norpregn-17(20)-ene 1; (3β,5α,17Z)-pregn-17(20)-ene 2, (3β,5α,16α,17E)-pregn-17(20)-en-16-ol 3, (16β,5α, 17E-pregn-17(20)-en-16-ol 4, (3β,5α,16β,17E)-pregn-17(20)-en-16- ol acetate 5, (3β,16α)-21-norpregna-5,17(20)-dien-16-ol 6, (3β,16α,17E)-pregna-5,17(20)-dien-16-ol 7, (3β,17Z)-pregna-5, 17(20)-diene 8, (3β,17E)-pregna-5,17(20)-dien-21-ol 9 and (3β,17E)-5,17(20)-dien-21-ol acetate 10. The oxygenated products (see Fig. 2) obtained from 1-10 and 1O2, generated by irradiation of Rose Bengal in 3O2-saturated pyridine solution, were characterized by 1H-, 13C-NMR, and MS (EI, FAB, HR-EI, ESI- and UV-MALDI-TOF) data. Major products were those formed by the ene reaction involving as intermediates the corresponding hydroperoxides and the cyclic tautomers of the allylic hydroperoxides, i.e., the corresponding oxiranium oxide-like intermediate (Scheme 5). |
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