Improved syntheses of shihunine, the spiro phthalide pyrrolidine alkaloid

Article abstract of DOI:10.1016/S0040-4020(01)82029-9

This paper describes the syntheses of the spire-alkaloid shihunine (0) by three different approaches. In the first, phthalic anhydride was condensed with N-methyl-2-pyrrolidone and the resulting phthalide 6 was hydrolysed to shihunine. In the second, phthalic anhydride was converted to the alkylidine phthalide 0 using Wittig reaction and then to 1 and finally to shihunine. In the third, methyl-2-formylbenzoate ( 6) was condensed with a zinc homoenolate to get the phthalide 0, which was then oxidised to 1,followed by cyclisation to the dilactone 4. 4 was converted to 1 through 5 and finally to shihunine.