Alpha-amination of labdane-type diterpenes by organocatalysis

The first electrophilic α-amination reaction of labdane-type diterpene (−)-(5S,9S,10S,13S)-labd-7-en-15-oic acid and (+)-(5S,8R,9R,10S,13R)-8-hydroxylabdan-15-oic acid, isolated from aerial parts of Ageratina jocotepecana is presented. In the presence of dibenzylazodicarboxylate and proline followed by an in situ reduction, the corresponding hydrazino alcohols were obtained. It is demonstrated that the first diterpene moiety had no influence in the diastereoselectivity that is then controlled by the catalyst used, at the opposite to the second diterpene that mainly control the diastereochemistry of the product.