1981 Volume 29 Issue 9 Pages 2557-2564
The naphthoquinone epoxide (4), derived from the naphthoquinone (1), is reduced with sodium borohydride under mild conditions to yield the cis-epoxy ketol (5) exclusively. The configuration of the 4-hydroxyl group in 5 is deduced on the basis of the intramolecular hydrogen-bonding observed in the infrared spectrum. Further reduction of 5 with sodium borohydride gives the cis-epoxyhydroxy lactone (7) as a main product, which is stereoselectively converted into the 10b-hydroxychelidonine (17) and 4b-epichelidonine analogs (19) by the following procedures : aminolysis with methylamine (7→13), reduction with lithium aluminum hydride (13→14), hydrogenolysis over a palladium catalyst (14→17), dehydration with mesyl chloride (17→18) and reduction with lithium aluminum hydride/aluminum chloride (18→19). The stereostructures for these compounds are deduced from the infrared and proton magnetic resonance data.
