ChemInform Abstract: Synthesis of Spirolactones by 1,3-Dipolar Cycloadditions to Methyl (S)-3-[(E)-Cyanomethylidene]-2-oxotetrahydrofuran-5-carboxylate

Dedicated to Professor Emeritus Miha Tisler on the occasion of his 75th birthday Treatment of methyl (S)-5-[(E)-(dimethylamino)methylidene]-2-oxotetrahydrofuran-5-carboxylate (2) with potassium cyanide in acetic acid gave (S)-5-[(E)-cyanomethylidene]-2-oxotetrahydrofuran-5-car-boxylate (3), which was used as chiral dipolarophile in 1,3-dipolar cycloadditions. Reactions of 3 with diazomethane (4) and nitrile oxides 5a-c afforded spirolactones 6–8 in 24-34% diastereomeric excess, while with diazomethane (4) in the presence of triethylamine, methyl 3-cyanomethyl-2-methoxyfuran-5-carboxylate (12) was obtained.