The synthesis of 1,2,4,5- and 1,2,9,10-tetrasubstituted and 1,2,4,5,8-pentasubsutituted pyrenes has been achieved by initially functionalizing the K-region of pyrene. Bromination, acylation, and formylation reactions afford high to moderate levels of regioselectivity, which facilitate the controlled introduction of other functional groups about 4,5-dimethoxypyrene. Access to 4,5-dimethoxypyren-1-ol and 9,10-dimethoxypyren-1-ol enabled a rare, C-2 primary alkyl substitution of pyrene.
The attempted dehydration of macrocyclic
α-ketols with the
Burgess reagent has resulted in the unexpected synthesis of carbamoylated,
bent para-phenylene units. The same reaction with
an acyclic analogue affords the intended dehydration product, indicating
that the change in reactivity is conformationally controlled and a
result of the bifunctional nature of the Burgess reagent.
The construction of the C(1) -C(5) fragment of the resorcylic acid lactone pochonin J is described. The synthesis is marked by the installation of the cis-1,3-diol moiety in a highly stereoselective manner using Evans' intramolecular base-catalyzed oxyconjugate addition of a hemiacetal-derived nucleophile. The synthetic route presented affords an efficient pathway to the preparation of this critical architectural feature that should facilitate the development of this secondary metabolite as a potential drug candidate.
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