4) The reaction of 6beta,7beta:15beta,16beta-dimethylene-4-androsten-3,17-dione (XIX) with 2-(1-ethoxyethoxy)-3-butenenitrile (XX) by means of BuLi and diisopropylamine (DIA) in THF gives the adduct (XXI), which is finally treated with LiBr and Li2CO3 in hot DMF .
3beta-Hydroxy-5-androsten-17-one (XVII) is dihydroxylated microbiologically by means of Colletotrichum lini to 3beta,7alpha,15alpha-trihydroxy-5-androsten-17-one (XVIII), which is treated with acetone and boron trifluoride etherate yielding the acetonide (XIX). Hydrolysis of (XIX) with HCl in methanol affords the 3beta,7beta,15alpha-isomer (XX), which is also obtained from (XVIII) by isomerization with perchloric acid in methylisobutylketone. Selective acylation of (XX) with pivaloyl chloride affords the 3beta,15alpha-dipivaloyloxy compound (XXI), which is submitted to cyclopropanation with trimethylsulfoxonium iodide and NaOH as before yielding (IX).
The acylation of spiro[pregnane-17,2'-tetrahydrofuran]-4,6,15-triene-3,5'-dione (I) with thioacetic acid in refluxing methanol gives the 7-acetylthio derivative (II), which is methylenated with trimethylsulfoxonium iodide and NaH in refluxing DMSO, yielding the 15beta,16beta-methylene derivative (III). Finally, this compound is dehydrogenated with 2,3-dichloro-5,6-dicyanobenzoquinone (IV) in refluxing benzene.
3) Reaction of 3beta-hydroxy-15beta,16beta-methylene-5-androsten-17-one (I) with 1-bromo-3,3-dimethoxypropane (XIII) and lithium in THF gives the 17alpha-(3,3-dimethoxypropyl) derivative (XIV), which by treatment with 70% acetic acid provides the spiro compound (XV). Oxidation of compound (XV) with cyclohexanone in the presence of (i-PrO)3Al and then treatment with 2N H2SO4 affords 15beta,16beta-methylene-3-oxo-17alpha-pregn-4-ene-21,17-carbolactone (XVI). Treatment of (XVI) with chloranil in t-BuOH yields the pregnadiene carbolactone (XVII), which is finally reacted with trimethylsulfoxonium iodide (XVIII) and NaH in DMSO.
Drospirenone can been obtained by different ways: 1) Fermentation of 3beta-hydroxy-15beta,16beta-methylene-5-androsten-17-one (I) with Botryodiplodia malorum gives the corresponding 7beta-hydroxy derivative (II), which is regioselectively acylated with pivaloyl anhydride and DMAP in pyridine to yield the 3beta-pivaloyloxy steroid (III). The epoxidation of (III) with tert-butylhydroperoxide catalyzed by VO(acetonylacetonate)2 complex affords the corresponding epoxide (IV), which is treated with PPh3 and CCl4 in dichloromethane to provide the 7alpha-chloro derivative (V). Reaction of (V) with Zn in AcOH/THF gives 5beta-hydroxy-3beta-(pivaloyloxy)-15beta,16beta-methylene-6-androsten-17-one (VI), which is hydrolyzed with KOH and NaClO4 in methanol/THF to provide 3beta,5beta-dihydroxy-15beta,16beta-methylene-6-androsten-17-one (VII). The cyclopropanation of (VII) with diiodomethane and Zn in hot ethylene glycol dimethylether gives 3beta,5beta-dihydroxy-6beta,7beta:15beta,16beta-dimethyleneandrostan-17-one (VIII), which is condensed with propargyl alcohol (IX) by means of EtOK in THF, yielding 17alpha-(3-hydroxy-1-propynyl)-6beta,7beta:15beta,16beta-dimethyleneandrostan-3beta,5beta,17beta-triol (X). The hydrogenation of (X) with H2 over either Pd/C in THF/methanol/pyridine (1) or Pd/CaCO3 in THF/2-propanol affords the corresponding 17alpha-(3-hydroxypropyl) derivative (XI), which is finally oxidized, lactonized and dehydrated by means of CrO3 in hot pyridine/water. Similar synthetic pathways have been described replacing the pivaloyl-protecting group with either tert-butyldimethylsilyl (TBDMS), dimethyl(3-methylbutyl)silyl or tribenzylsilyl groups: 2) Alternatively, the 17alpha-(3-hydroxypropyl) derivative (XI) can be oxidized with RuCl3 and NaBrO3 in hot acetonitrile/water to give the 3-hydroxyspirolactone (XII), which is finally dehydrated by means of TsOH in THF.
This compound has been obtained by different ways: 1. The fermentation of 3beta-hydroxy-15beta,16beta-methylene-5-androsten-17-one (I) or 3beta-acetoxy-15beta,16beta-methylene-5-androsten-17-one (II) with Botryodiplodia malorum gives the corresponding 3beta,7beta-dihydroxy derivative (III), which is regioselectively silylated with Tbdms-Cl and imidazole to yield the 3-beta-silylated compound (IV). The epoxidation of (IV) by means of tert-butyl hydroperoxide catalyzed by VO(acetonylacetonate)2 complex affords the corresponding epoxide (V), which is treated with PPh3 and CCl4 in dichloromethane to provide the 7-alpha-chloro derivative (VI). The desilylation of (VI) with HCl in THF/methanol gives the 3beta-hydroxy compound (VII), which is treated with Zn in AcOH/THF to yield 3beta, 5beta-dihydroxy-15beta,16beta-methylene-6-androsten-17-one (VIII) (1). The cyclopropanation of (VIII) with diiodomethane and Zn in hot ethyleneglycol dimethylether gives 3beta,5beta-dihydroxy-6beta,7beta:15beta,16beta-bismethyleneandrostan-17-one (IX), which is condensed with propargyl alcohol (X) by means of K-OEt in THF, yielding 17alpha-(3-hydroxy-1-propynyl)-6beta,7beta:15beta,16beta-bismethyleneandrostan-3,5beta,17beta-triol (XI). The hydrogenation of (XI) with H2 over Pd/C in THF/methanol/pyridine affords the corresponding 17alpha-(3-hydroxypropyl) derivative (XII), which is finally oxidized, lactonized and dehydrated by means of CrO3 in hot pyridine/water. 2. Alternatively, the 17alpha-(3-hydroxypropyl) derivative (XII) can be oxidized with RuCl3 and NaBrO3 in hot acetonitrile/water, giving the hydroxy carbolactone (XIII), which is finally dehydrated by means of Ts-OH in THF. 3. Similar synthetic pathways have been described replacing the Tbdms protecting group with either dimethyl(3-methylbutyl)silyl or tribenzylsilyl groups.
4. The fermentation of 3beta-hydroxy-15beta,16beta-methylene-17alpha-pregn-5-ene-21,17-carbolactone (I) with Botryodiplodia malorum gives the corresponding 3beta,7beta-dihydroxy derivative (II), which is regioselectively silylated with Tbdms-Cl and imidazole to yield the 3-beta-silylated compound (III). The epoxidation of (III) by means tert-butyl hydroperoxide catalyzed by VO2 acetonylacetonate complex affords the corresponding epoxide (IV), which is treated with PPh3 and CCl4 in dichloromethane to provide the 7-alpha-chloro derivative (V). The desilylation of (V) with HCl in THF/methanol gives the 3beta-hydroxy compound (VI), which is treated with Zn in AcOH/THF to yield 3beta, 5beta-dihydroxy-15beta,16beta-methylene-17alpha-pregn-6-ene-21,17-carbolactone (VII). The cyclopropanation of (VII) with diiodomethane and Zn in hot ethyleneglycol dimethylether gives 3beta,5beta-dihydroxy-6beta,7beta:15beta,16beta-bismethylene-17-alpha-pregnan-21,17-carbolactone (VIII), which is finally oxidized and dehydrated by means of CrO3 in hot pyridine/water.