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|Title:||Biomimetic radical polycyclizations of isoprenoid polyalkenes initiated by photoinduced electron transfer|
|Abstract:||Isoprenoid polyalkene radicals, formed by anti- Markovnikov addition of a nucleophile to their parent radical cations, which are readily accessible via photoinduced electron transfer, undergo cascade cyclizations. The regioselectivity is efficiently controlled by the substitution pattern, i.e., the generally observed 6-endo-trig mode is replaced by 5-exo-trig, if electron-deficient double bonds (e.g. 1, 1-dicyanovinyl groups) are involved. Moreover, remarkably high asymmetric inductions have been achieved by the use of chiral spirocyclic dioxinones, derived from the chiral auxiliary (-)-menthone, notably remotely located from the initiationsite ofthe cyclizations.These asymmetricphotoinduced cyclizations constitute strong evidence of spontaneous coiling/folding of the terpenoid polyalkene chain and give ready access to the enantiomerically pure tricyclic terpenoids of complementary chiralities by means of the single chiral auxiliary (-)-menthone.|
|Appears in Collections:||IJC-A Vol.36A(06) [June 1997]|
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