Factors governing the relative stabilities of the C/D cis and trans ring junctures in .DELTA.8-11-keto steroids

Stereochemical course of the chemical and catalytic reduction of 11-oxo-5.alpha.,14.beta.-cholest-8-en-3.beta.-ol. Synthesis of 8.alpha.,9.alpha.,14.beta.-, 8.alpha.,9.beta.,14.beta.-, and 8.beta.,9.alpha.,14.beta.-steroids

“…The lithium-ammonia reduction of this labeled compound as described previously provided, after purification, 2a which had physical and spectroscopic properties consistent with unlabeled 2: NMR 3.97 (br d, 1 H, lla-H, J = 5 Hz), 3.60 (3a-H, W1/2 * 22 Hz), 0.95 (s, 3 H, CH3), 0.90 (s, 3 H, CH3); mass spectrum, m/z (rel. intensity) 391 (36), 376 (30), 358 (7), 307 (4), 306 (4), 278 (38), 260 (7), 223 (21), 208 (26), 194 (100). 5a,8a,l4/S-Cholestane-3/8,ll/8-diol Di-p-bromo benzoate (2b).…”

“…1 = present work, MS-9 (probe); 2 = Mulheirn and Ryback,5a AEI MS-30 (GC inlet); 3 = Mulheirn and Ryback,5c MS-9 (probe); 4 = Seifert and Moldowan,6 GC/MS (40 eV), Nuclide 12-90-G, these authors have assigned stereochemistries based on mass spectra and GC retention times. C and/or B for compounds 4,6,7,9,10, and 13 may be due to the change in hybridization (sp? to sp2) at C-11.…”

“…Recently we had cause to prepare the 8-11-ketone 1 in a study of the effect of the 173-alkyl group on the relative stabilities of the C/D cis and trans ring junctures. 7 Additionally, this compound was to serve as an intermediate in the synthesis of certain deuterium labeled steroidal 83,9a,143-hydrocarbons needed for mass spectral studies. A key reaction in these labeling experiments was to be the lithium-ammonia reduction of 1, which was expected to give the "natural" 83,9a B/C ring juncture based on the results of previous studies with steroidal sapogenins.8 The unexpected results of the lithium-ammonia reduction of the unsaturated ketosterol 1 prompted subsequent experimental work to establish the stereochemistry of the B/C ring juncture as depicted in Scheme I.…”

“…The Jones oxidation of 2 and 3 to the diketones 4 and 6 presumably took place without epimerization at C-9. This method has been used previously for oxidation of alcohols to enolizable ketones without epimerization of a chiral center a to the ketone function.14 Subsequent base-catalyzed equilibration of 6 gave an equilibrium mixture consisting of 73% 6 and 27% 93 epimer 9.15 Likewise, equilibration of the catalytic hydrogenation product 7 gave an equilibrium mixture consisting of 74% 7 and 26% 93 epimer 10. 15 The diketones 6 and 9 as well as the monoketones 7 and 10 show large differences in their mass spectral fragmentation patterns from the "normal" (83,9a) B/C ring juncture diketone 4 (143 configuration), which in turn is quite different from the "normal" (83,9 ,14 ) diketone 19.…”

Surface photochemistry: silica gel as a medium for photochemical cycloaddition of enones to aliene

“…The photocycloaddition of enones (7,9,11,13,15, and 17) to allene in methylene chloride gave (H/H) regioisomers as major photoadducts with the (HIT) regioisomers present in small amounts, as shown by I3Cmr. In contrast, irradiation of these enones and allene on silica produced a pronounced shift Presumably the change is caused by changes in electron distribution induced by adsorption onto the silica gel surface, but no evidence is presently available to distinguish between these possibilities.…”