Lu. Roman et al., Generation of the new quirogane skeleton by a vinylogous retro-Michael type rearrangement of longipinene derivatives, TETRAHEDRON, 57(34), 2001, pp. 7269-7275
A new tricyclic hydrocarbon skeleton, named quirogane, was prepared by a vi
nylogous retro-Michael type molecular rearrangement of (4R,5S,7R,8R,9S,10R,
11R)-7,8-diacetyloxy-9-mesyloxy-1-oxolongipin-2-ene (5). A remarkable diffe
rence in chemical behavior as compared to the corresponding 2,3-dihydroderi
vative of 5 is explained in terms of the stability of anionic intermediates
, which were evaluated by AMI calculations. The structure of the quirogane
skeleton was confirmed by single crystal X-ray diffraction analysis of quir
ogadiene 6. A [2+2] photochemical cyclization of 6 afforded the highly stra
ined pentacyclic sesquiterpenoid (10). (C) 2001 Elsevier Science Ltd. All r
ights reserved.