Publications (4)19.32 Total impact
Article: Enantioselective synthesis of (+)-monobromophakellin and (+)-phakellin: a concise phakellin annulation strategy applicable to Palau'amine.Angewandte Chemie International Edition 02/2008; 47(7):1284-6. · 13.45 Impact Factor
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ABSTRACT: Highly diastereoselective, substrate-controlled, halogenation/ring contraction sequences delivered the naturally occurring chlo-rinated and unnatural brominated and iodinated axinellamine core structure. An unexpected azide displacement of the chlorinated cyclopen-tane, which proceeded with retention of stereochemistry, suggested a modification of the Scheuer/Kinnel proposal that may account for the related natural product massadine. Two unsuccessful routes to access the stereochemistry proposed for palau'amine were S N 2 displacement of the bromo-and iodocyclopentane with excess chloride anion and an intramolecular directed chlorination pathway. Finally, an unexpected chlorination during our phakellstatin synthesis proceeded with retention of stereochemistry during tosylation possibly resulting from neigh-boring group participation.04/2006;
Article: Highly regioselective Diels-Alder reactions toward oroidin alkaloids: use of a tosylvinyl moiety as a nitrogen masking group with adjustable electronics.[show abstract] [hide abstract]
ABSTRACT: [reaction: see text] The use of the p-toluenesulfonyl (Ts) and tosylvinyl (Tsv) groups as nitrogen masking groups imparted high regioselectivity in Diels-Alder reactions directed toward members of the oroidin-derived marine alkaloid family. The electron-withdrawing Tsv group was utilized as an electronically adjustable nitrogen-protecting group as subsequent hydrogenation provided the more electron-rich tosylethyl (Tse) group. This electronic adjustment strategy avoided a protecting group exchange and provided the required electronics for the key chlorination/ring-contraction sequence.Organic Letters 05/2005; 7(9):1679-82. · 5.86 Impact Factor
Article: A unified synthetic strategy toward oroidin-derived alkaloids premised on a biosynthetic proposal[show abstract] [hide abstract]
ABSTRACT: Details of the evolution of a synthetic strategy toward the spirocyclic chlorocyclopentane core of oroidin-derived alkaloids, in-cluding the axinellamines and potentially adaptable to palau'amine, are described. A proposed refinement of the Kinnel–Scheuer biosynthetic proposal for palau'amine is posited. Studies undertaken to improve the regioselectivity and efficiency of a key Diels–Alder reaction utilizing a novel protecting group strategy, microwave chemistry, and other strategies are described. Further insights regarding the suitability of dif-ferent protecting groups during the epoxidation/chlorination/ring contraction sequence are disclosed. Several interesting by-products from this reaction sequence are reported. These studies have led to a unified synthetic strategy to the axinellamines and palau'amine.