Synthetic transformations of higher terpenoids: XX. Synthesis and transformations of diterpene ureido esters
摘要:
Lossen rearrangement of N-hydroxymaleopimaric acid amide p-toluenesulfonate in the presence of amines in methanol led to the formation of the corresponding diterpene ureido esters with high regio- and stereoselectivity. Treatment of the resulting ureides with phosphoryl chloride gave cyclic amidines via intramolecular ring closure. Substituted hydantoins were obtained by reactions of the ureido esters with glyoxal in acid medium, and their treatment with sodium ethoxide in ethanol afforded compounds of the naphtho[1,2-h]-quinazoline series.