A minimalist NMR approach for the structural revision of mucoxin.

In an attempt to revise the structural assignment of mucoxin, and faced with 64 diastereomeric possibilities, we resorted to the synthesis of truncated structures that contained the core stereochemical sites. Twelve stereochemical analogues were synthesized, their (1)H and (13)C NMR spectra were analyzed and four recurring stereochemical trends were distilled from the data. Applying the observed trends to the diastereomeric population pared the possible choices for the correct structure of mucoxin from 64 to 4.

Skeletal diversity via cationic rearrangements of substituted dihydropyrans.

Substituted dihydropyrans, easily accessed from a commercially available glycal, undergo acid-catalyzed rearrangement to provide highly functionalized isochroman and dioxabicyclooctane scaffolds.

Synthesis of Substrates and Biochemical Probes for Study of the Peptidoglycan Biosynthetic Pathway.

Several widely used antibiotics such as beta-lactams, glycopeptides, and lipoglycopeptides exhibit their activity by interfering with peptidoglycan biosynthesis. Ever-increasing resistance to these and other agents has placed a renewed emphasis on the need to understand the reactions in this bio-synthetic pathway at the molecular level. While efficient access to many of the biosynthetic enzymes has been gained, the isolation of their natural substrates has proven difficult.

Synthesis of the proposed structure of mucoxin via regio- and stereoselective tetrahydrofuran ring-forming strategies.

An enantioselective total synthesis of the proposed structure of mucoxin (1) is described. Mucoxin, an annonaceous acetogenin isolated from bioactive leaf extracts of Rollinia mucosa, is the first acetogenin containing a hydroxylated trisubstituted tetrahydrofuran (THF) ring. This natural product is a highly potent and specific antitumor agent against MCF-7 (breast carcinoma) cell lines (ED50 = 3.

Versatile and stereoselective syntheses of orthogonally protected beta-methylcysteine and beta-methyllanthionine.

[reaction: see text] Lantibiotics are a class of lanthionine (and/or beta-methyllanthionine)-containing peptides with antibioitic activity against Gram-positive bacteria. As part of our research effort directed toward the synthesis and mechanistic study of the lantibiotic peptide mersacidin (1), we report stereoselective syntheses of orthogonally protected beta-methylcysteine (beta-MeCys) and beta-methyllanthionine (beta-MeLan), two key nonnatural amino acid components of the mersacidin architecture.

One-pot regio- and stereoselective cyclization of 1,2,n-triols.

A simple and efficient process to cyclize triols containing a 1,2-diol functionality with a pendant hydroxyl group is presented. The one-pot procedure converts the 1,2-diol into an ortho ester in situ, which upon treatment with a Lewis acid generates a cyclic acetoxonium intermediate. This intermediate is subsequently trapped by the pendant hydroxyl group to generate a cyclic ether.

Osmium tetroxide-promoted catalytic oxidative cleavage of olefins: an organometallic ozonolysis.

A mild, organometallic alternative to ozonolysis utilizing oxone and OsO(4) is presented. This is a direct oxidation of olefins via the carbon-carbon cleavage of an osmate ester by the action of oxone. Twenty-four different olefins were converted to their corresponding ketones or carboxylic acids in high yields (>80%).