Regioselective synthesis of .DELTA.6-, .DELTA.7-, and .DELTA.8-14.alpha.-cyanosterol derivatives: versatile precursors to 14.alpha.-demethylase inhibitors
摘要:
The efficient preparation of 3-beta-(benzoyloxy)-4,4-dimethyl-5-alpha-cholest-8(14)-en-7-one (4a) and 3-beta-benyloxy)-5-alpha-ergost-8(14)-en-7-one (4b) and their conversion to DELTA-6-, DELTA-7- or DELTA-8-14-alpha-functionalized sterols is reported. The alkylaluminum-mediated 1,4-addition of HCN (Nagata reaction) to enones 4a,b is used to introduce the 14-alpha-substituent. Reduction of these conjugate addition products (5a,b) affords the 7-alpha-hydroxysterols (6a,b). The dehydration of 6a with Martin sulfurane reagent regioselectively produces the DELTA-6-14-alpha-cyanosterol 8. Alternatively, mesylation of 6a and elimination affords a mixture of DELTA-7:DELTA-6-sterols (3:1) from which the DELTA-6-sterol is removed by selective ozonolytic degradation. The ozonolytic stability of the DELTA-7-14-alpha-cyanosterols is also exploited in the preparation of 14-alpha-cyanosterols possessing modified side chains. Ozonolysis of 3-beta-(benzoyloxy)-5-alpha-ergost-7,22-diene-14-alpha-carbonitrile (9b) gave 18, which is used to prepare compounds containing the "24 methenyl" (21) and "lanosterol" (23) side chains. The trapping of the intermediate aluminum enolate formed in the hydrocyanation of 4a gives an 8-beta-bromosterol 13. Dehydrobromination of 13 provides a novel regioselective synthesis of the difficult to prepare DELTA-8-14-alpha-functionalized sterol 14.
Regioselective synthesis of .DELTA.6-, .DELTA.7-, and .DELTA.8-14.alpha.-cyanosterol derivatives: versatile precursors to 14.alpha.-demethylase inhibitors
摘要:
The efficient preparation of 3-beta-(benzoyloxy)-4,4-dimethyl-5-alpha-cholest-8(14)-en-7-one (4a) and 3-beta-benyloxy)-5-alpha-ergost-8(14)-en-7-one (4b) and their conversion to DELTA-6-, DELTA-7- or DELTA-8-14-alpha-functionalized sterols is reported. The alkylaluminum-mediated 1,4-addition of HCN (Nagata reaction) to enones 4a,b is used to introduce the 14-alpha-substituent. Reduction of these conjugate addition products (5a,b) affords the 7-alpha-hydroxysterols (6a,b). The dehydration of 6a with Martin sulfurane reagent regioselectively produces the DELTA-6-14-alpha-cyanosterol 8. Alternatively, mesylation of 6a and elimination affords a mixture of DELTA-7:DELTA-6-sterols (3:1) from which the DELTA-6-sterol is removed by selective ozonolytic degradation. The ozonolytic stability of the DELTA-7-14-alpha-cyanosterols is also exploited in the preparation of 14-alpha-cyanosterols possessing modified side chains. Ozonolysis of 3-beta-(benzoyloxy)-5-alpha-ergost-7,22-diene-14-alpha-carbonitrile (9b) gave 18, which is used to prepare compounds containing the "24 methenyl" (21) and "lanosterol" (23) side chains. The trapping of the intermediate aluminum enolate formed in the hydrocyanation of 4a gives an 8-beta-bromosterol 13. Dehydrobromination of 13 provides a novel regioselective synthesis of the difficult to prepare DELTA-8-14-alpha-functionalized sterol 14.
Regioselective synthesis of .DELTA.6-, .DELTA.7-, and .DELTA.8-14.alpha.-cyanosterol derivatives: versatile precursors to 14.alpha.-demethylase inhibitors
作者:Timothy F. Gallagher、Jerry L. Adams
DOI:10.1021/jo00038a024
日期:1992.6
The efficient preparation of 3-beta-(benzoyloxy)-4,4-dimethyl-5-alpha-cholest-8(14)-en-7-one (4a) and 3-beta-benyloxy)-5-alpha-ergost-8(14)-en-7-one (4b) and their conversion to DELTA-6-, DELTA-7- or DELTA-8-14-alpha-functionalized sterols is reported. The alkylaluminum-mediated 1,4-addition of HCN (Nagata reaction) to enones 4a,b is used to introduce the 14-alpha-substituent. Reduction of these conjugate addition products (5a,b) affords the 7-alpha-hydroxysterols (6a,b). The dehydration of 6a with Martin sulfurane reagent regioselectively produces the DELTA-6-14-alpha-cyanosterol 8. Alternatively, mesylation of 6a and elimination affords a mixture of DELTA-7:DELTA-6-sterols (3:1) from which the DELTA-6-sterol is removed by selective ozonolytic degradation. The ozonolytic stability of the DELTA-7-14-alpha-cyanosterols is also exploited in the preparation of 14-alpha-cyanosterols possessing modified side chains. Ozonolysis of 3-beta-(benzoyloxy)-5-alpha-ergost-7,22-diene-14-alpha-carbonitrile (9b) gave 18, which is used to prepare compounds containing the "24 methenyl" (21) and "lanosterol" (23) side chains. The trapping of the intermediate aluminum enolate formed in the hydrocyanation of 4a gives an 8-beta-bromosterol 13. Dehydrobromination of 13 provides a novel regioselective synthesis of the difficult to prepare DELTA-8-14-alpha-functionalized sterol 14.