Synthesis of the C1-C20 and C15-C27 segments of aplyronine A.

The synthesis of C1-C20 and C15-C27 segments of Aplyronine A is described. Oxidative cleavage of cyclic vinyl sulfones has been used to prepare key fragments of Aplyronine A. Key precursors are united by Horner-Wadsworth-Emmons and Julia-Kociensky olefination for the respective elaboration of the C1-C20 and C15-C27 segments.

Chemoselective and enantioselective oxidation of indoles employing aspartyl peptide catalysts.

Catalytic enantioselective indole oxidation is a process of particular relevance to the chemistry of complex alkaloids, as it has been implicated in their biosynthesis. In the context of synthetic methodology, catalytic enantioselective indole oxidation allows a rapid and biomimetic entry into several classes of alkaloid natural products. Despite this potentially high utility in the total synthesis, reports of catalytic enantioselective indole oxidation remain sparse. Here we report a highly chemoselective catalytic system for the indole oxidation that delivers 3-hydroxy-indolenines with good chemical yields and moderate to high levels of enantio- and diastereoselectivity (up to 95:5 er and up to 92:8 dr). These results represent, to our knowledge, the most selective values yet reported in the literature for catalytic asymmetric indole oxidation. Furthermore, the utility of enantioenriched hydroxy-indolenines in stereospecific rearrangements is demonstrated.

Second-generation synthesis of syn- and anti-cycloheptadienylsulfone polyketide stereodiads.

Stereodiad sulfones 18a and 18b are key intermediates for polyketide synthesis. This note describes the synthesis of 18a and 18b from enantiopure epoxide 2. The two sequences have been optimized for large-scale synthesis to give 80-85% overall yields in one operation (one operation implies that no crystallization or distillation is required throughout the synthesis) while avoiding chromatography.

Conversion of cyclic vinyl sulfones to transposed vinyl phosphonates.

Functionalized cyclic vinyl sulfones were directly converted to the "polarity reversed" vinyl phosphonates through an efficient one pot procedure. Ozonolysis of these vinyl sulfones and vinyl phosphonates furnish complementary sets of termini-differentiated ester-aldehydes. This strategy has been applied for preparation of segments needed for the synthesis of Aplyronine A. The scope and limitations of this transformation were defined.