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5‐Substituted (S)‐tetrahydrofuran‐2‐ones (1a,b) and (S)‐pyrrolidin‐2‐ones (1c,d) were transformed in three steps, by treatment with tert‐butoxybis(dimethylamino)methane (Bredereck's reagent), followed by nitrosation and stereoselective catalytic hydrogenation, into the corresponding 5‐substituted (3S,5S)‐3‐acetylaminotetrahydrofuran‐2‐ones (4a,b) and (3S,5S)‐3‐acetylaminopyrrolidin‐2‐ones (4c,d).

Dedicated to Professor Emeritus Miha Tišler on the occasion of his 75th birthdayTreatment 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-carboxylate (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.

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