Scandium-Catalyzed Skeleton Conversion of Lathyrane to Lathyranone-Type Euphorbia Diterpenes.

Naturally occurring 1(15 → 14) abeo -lathyrane rearrangement-type diterpene lathyranone A ( 1 ) was prepared from lathyrane-type Euphorbia factor L 11 ( 1a ) via an efficient Sc(OTf) 3 /Et 2 NH-catalyzed α-ketol rearrangement, which was also suitable for the synthesis of lathyranones 2 and 3 . This skeletal conversion strategy had the characteristic of biogenetically patterned synthesis and provided a convenient method for accessing naturally rare functionalized lathyranones from lathyranes. Moreover, the absolute configuration of the lathyranone skeleton was confirmed for the first time by the X-ray diffraction of 2 .