Abstract Regioselective reduction of unsymmetrically substituted spiroanhydrides (A 1 and 3) with reducing agents such as sodium boranate, lithium boranate, dimethylamine borane and lithium-or potassium-tri-(sec-butyl) boranate yielded the spirocyclic lactones 1 and 2 or 4 and 5, respectively. The influence of the temperature and the sequence of addition of reducing agents on the ratio of the spirocyclic lactones formed was studied in order to ...
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