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Evolution of the synthetic strategy that culminated in the first total syntheses of the structurally unique plectosphaeroic acids B (2) and C (3) is described. The successful enantioselective route to (+)-2 and (+)-3 proceeds in 6 and 11 steps from the known hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione 39, which in turn is available in enantiomerically pure form by chemical synthesis. The central challenge in this synthesis endeavor was uniting the hexahydro-2H-pyrazinopyrrolo[2,3-b]indole-1,4-dione and cinnabarinic acid fragments of these marine alkaloids. Critical for achieving this successful C-N bond formation was the use of an iodocinnabarinic acid diester in which the amino group was masked with two Boc substituents, a Cu(I) carboxylate complex and the weak base KOAc. The highly congested C-N bond generated in this coupling, in conjunction with the delicate nature of the densely functionalized coupling partners, provided a striking testament to the power of modern copper-mediated amination methods. Two approaches, one stereoselective, for introducing the methylthio substituents of (+)-plectosphaeroic acid B were developed. The epitrisulfide ring of (+)-plectosphaeroic acid C was formed by ring expansion of an epidisulfide precursor. [ABSTRACT FROM AUTHOR]

The first total synthesis of a member of the plectosphaeroic acid family of fungal natural products is reported. Key steps include the late-stage formation of the hindered N6-C9" bond and stereoselective introduction of the two methylthio substituents. [ABSTRACT FROM AUTHOR]

A concise second-generation total synthesis of the fungal derived alkaloid ( + )-gliocladin C ( l l ) in 10 steps and 11% overall yield from isatin is reported. In addition, the epipolythiodioxopiperazine (ETP) natural product ( + )-gliocladine C (6) has been prepared in six steps and 29% yield from the di-(-test-butoxycarbonyl) precursor of 11. The total synthesis of 6 constitutes the first total synthesis of an ETP natural product containing a hydroxyl substituent adjacent to a quaternary carbon stereo-center in the pyrrolidine ring. [ABSTRACT FROM AUTHOR]