Steroidal Cyclic Ketals. XII.¹ The Preparation of Δ¹⁶-Steroids

Expeditious Synthesis of Hippuristanol and Congeners with Potent Antiproliferative Activities

“…A rearranged compound (S1) [10] was detected in trace amount, which had been the major product upon treatment of 10 with SOCl 2 in pyridine at room temperature. [11] It is worth noting that a substrate without the benzoyl protection at the 11-OH (namely, 3a-benzoyloxy-11b,17a-dihydroxy-5apregn-20-one) gave rise to the corresponding enone and rearranged product in nearly 1: 1 ratio upon treatment with semicarbazide (data not shown).…”

Stereoelectronic effects in hydrogen-atom transfer reactions of substituted cyclohexyl radicals

“…Since each contains one tertiary and two secondary p-hydrogen atoms the statistical factor is the same for disproportionation of both of the radicals (14) and (16). Nor can the difference in the ratios of cyclohexenes, (28) : (25) and (30) : (25), formed respectively from the radicals (14) and (16) be attributed to steric or thermodynamic factors. Steric interactions should disfavour abstraction of axial p-hydrogen atoms from either radical (14) or (16) but particularly from the latter because of the proximity of the reaction centre to the axial methyl substituent.…”

“…This is observed more directly in the formation of the cyclohexene (27) from the tosylate (32h). Pure samples of the olefins ( 25) and (28) were obtained from product mixtures by chromatography on silver nitrate-impregnated silica gel. A pure sample of the olefin (30) was similarly separated from the mixture with the olefin (25) obtained by base treatment of the tosylate (3%).…”

Directed Dilithiation of Diaryl Compounds: Preparation of Tricyclic Pharmaceuticals Based on the Dibenzoheteroazepine Skeleton

“…12 Extensive reviews have been written by Gschwend 13 and Snieckus 10 on the application of this DoM process. The tricyclic compound 10a was subsequently dehydrated using thionyl chloride and pyridine 18 11a, 70% 14 However, most of the work done thus far has been on mono-lithiated species, while our approach involves the utilization of a dilithio-diaryl species as a key intermediate.…”