Upon irradiation of an ethanolic solution of 3β‐hydroxy‐11‐oxo‐lanostane(1) with ultraviolet light and subsequent acetylation of the crude reaction mixture, a single tertiary alcohol, the 11,18‐cyclobutanol derivative 4, could be isolated in about 40% yield (corrected for recovered starting material). According to previous findings[4] and in contrast to this result, the steroidal 4,4‐dimethyl‐ketone 15 is exclusively converted into the 11,19‐cyclobutanol 16. It is assumed that the additional methyl group in the 14α position of 1 causes this shift of the selective attack in the photo‐chemical cyclization process from CH3‐19 to CH3‐18.

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Methyl sterculate was isolated from an irradiation mixture obtained by photolysis of diazomethane in presence of methyl stearolate by column chromatography on silicic acid. The separable amount of the photoproduct was 9.5%. The presence of the cyclopropene structure was proved by spectroscopy and chemical methods.

Stearolsäuremethylester (I) wurde mit Diazomethan unter Belichtung mit einer Quecksilberlampe umgesetzt.

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