3-[(E)-4-methoxycarbonylbutylidene]bicyclo[3,3,0]octan-2-one → 3-[(Z)-4-methoxycarbonylbutylidene]bicyclo[3,3,0]octan-2-one

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Reaction Steps

A solution of 6-[(E)-(mixture of 3α and 3β)-hydroxyoct-1-enyl]-3-[(E)-4-methoxycarbonylbutylidene]bicyclo[3,3,0]octan-2-one (20 mg), prepared as described in Example 4 and predominantly in the 6β-configuration, otherwise known as (±)-methyl(5E,13E)-(9S),[mixture of (15R) and (15S)]-6a-oxo-6,9-methano-15-hydroxyprosta-5,13-dienoate, in methanol (5 ml) was irradiated for 20 hours with ultra-violet rays of wavelength 254 nm, emitted by a low pressure mercury vapour lamp. The solution was carefully concentrated in vacuo and then subjected to preparative thin layer chromatography on silica gel, using a mixture of ethyl acetate and hexane (1:4 v/v) as eluant, to give 6-[(E)-(mixture of 3α and 3β)-hydroxyoct-1-enyl]-3-[(Z)-4-methoxycarbonylbutylidene]bicyclo[3,3,0]octan-2-one (5.0 mg), predominantly in the 6β-configuration, otherwise known as (±)-methyl(5Z,13E)-(9S),[mixture of (15R) and (15S)]-6a-oxo-6,9-methano-15-hydroxyprosta-5,13-dienoate [NMR in deuterochloroform: multiplets at 5.9, 5.5., 4.1, 3.0-1.1, 1.1-0.7 p.p.m., singlet at 3.7 p.p.m.]; and recovered 6-[(E)-(mixture of 3α and 3β)-hydroxyoct-1-enyl]-3-[(E)-4-methoxycarbonylbutylidene]-bicyclo[3,3,0]octan-2-one (3.6 mg) [NMR in deuterochloroform: multiplets at 6.5, 5.5, 4.1, 3.0-1.1, 1.1-0.7 p.p.m., singlet at 3.7 p.p.m⟧

Provenance & Evidence