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Lewis acids control regioselectivity in the alkylation of epi-chlorohydrin and the stereochemistry of an alkyne addition to set the C24/C23 anti relationship. These advances facilitate an efficient total synthesis of bullatacin in 13.3% overall yield from commercial starting materials.

Analysis of the extracts of male ants of Monomorium minimum and M. ebeninum, by GC-MS and GC-FTIR revealed the presence of tyramides 2 and 4c, for which the structures were established by comparison with synthetic samples. These compounds and their analogs 1 and 3 were also found in males of other Monomorium species, males of Myrmicaria opaciventris, and males of several Solenopsis (Diplorhoptrum) species. Vapor-phase FTIR spectra revealed critically important structural clues to two of the tyramides, which had methyl-branching in the tyramide acyl moiety. Tyramide 4c exhibited a strong intramolecular amide NH hydrogen bond where an α-keto group was deduced to be present in the acyl moiety and also showed the overlap of this ketone group frequency with that of the amide νC=O. The biological function of these compounds is uncertain; however their role in ant-mating behavior may be suggested by a large body of evidence.

The aerobic oxidation of 5-hydroxy pentenes to trans-tetrahydrofurans (THFs), the Mukaiyama oxidation, has in recent years emerged as a powerful tool in synthetic chemistry. In this report we describe the first crystal structures of 2,4-dioxo-alkanoic acid dialkylamide complexes for both Co(II) and Co(III) salts. The Co(II) structures show an unprecedented arrangement of atoms, with a central Co(II)(H2O)6 flanked by two Co(II) atoms each coordinated with three anionic chelating ligands. The dimeric Co(III) structures show two anionic chelating ligands and bridging hydroxyl groups.Key words: aerobic oxidation, trans-tetrahydrofuran (THF), cobalt, X-ray crystallography, oxidation, coordination.

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[reaction: see text] A new, convenient, one-pot protocol is described for oxidation of zirconocyclopent-2-enes selectively at the sp(3) carbon by efficient transfer to electrophilic ((c)Hex)(2)BCl followed by oxidation with H(2)O(2)/NaOH to afford 1-alkylidene-2-hydroxymethylcyclopentanes. Results with several substrates show that overall reaction efficiencies for the zirconocene-mediated enyne cyclization, boron transmetalation, and oxidation sequence are generally comparable to yields obtained from protonation of intermediate zirconocycles. The formation of E/Z olefin isomers from the cyclization-oxidation sequence and an acid-catalyzed pinacol-type rearrangement of a vinylsilane are described.

Selective Oxidation of Zirconocyclopentenes via Organoboranes. -The title reaction represents a novel, convenient, one-pot protocol using the efficient transfer to electrophilic Cy2BCl followed by oxidation with H2O2/NaOH to afford a broad spectrum of cyclopentane products. The overall reaction efficiencies are comparable to yields obtained from protonation of intermediate zirconocycles. -(GORMAN, J. S. T.; IACONO, S. T.; PAGENKOPF*, B. L.; Org. Lett. 6 (2004) 1, 67-70; Dep. Chem. Biochem., Univ. Tex., Austin, TX 78712, USA; Eng.) -Steudel 23-086 2004 Cyclopentane derivatives