- Synthesis and characterization of novel spirooxazacamphorsultam derivatives
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Derivatives of camphorsultam which contain novel spirooxazolidine and spirooxazine structures have been prepared in high yield and purity. Though it was expected that the ketone moiety would undergo acetal formation, the imine instead underwent reaction and was proven by X-ray crystallography and 2D NMR techniques. The initial ketone-containing derivatives were then reduced to produce exo-hydroxy analogs that have potential as a new family of chiral auxiliaries.
- Wilke, Burkhardt I.,Goodenough, Angela K.,Bausch, Cory C.,Cline, Erika N.,Abrams, M. Leigh,Fayer, Effrat L.,Cermak, Diana M.
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- Chemistry of Oxaziridines. 16. A Short, Highly Enantioselective Synthesis of the AB-Ring Segments of γ-Rhodomycinone and α-Citromycinone Using (+)-oxaziridine
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A highly efficient procedure for the preparation of rhodomycinone 1 AB synthons (-)-2a and (+)-2b in high enantiomeric purity (93-4percent ee) and good yield is described.This method involves asymmetric oxidation of the lithium enolate of 2-ethyl-5,8-dimethoxy-1-tetralone (4) with (+)-oxaziridine (5c), a new enantiomerically pure, aprotic oxidizing reagent.Lower stereoselectivities were observed with this reagent for the enantioselective oxidation of 2-substituted 1-tetralone enolates 8 lacking the 8-methoxy group.
- Davis, Franklin A.,Kumar, Anil,Chen, Bang-Chi
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- Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds
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Compounds containing two alkyne groups in close vicinity at the rigid skeleton of camphorsulfonamide show unique reactivities when treated with electrophiles or catalytic amounts of platinum(II). The formed product structures depend not only on the reagents used but also on the substituents attached to the triple bonds. Cycloisomerisations with perfect atom economy lead to polycyclic heterocycles that resemble to some extent the AB ring system of paclitaxel. Herein, we present practical synthetic methods for the selective synthesis of precursor dialkynes bearing different substituents (alkyl, aryl) at the triple bonds, based on ketals or an imine as protecting groups. We show for isomeric dialkynes that the reaction cascade induced by Pt(II) includes ring annulation, sulphur reduction, and ring enlargement. One isomeric dialkyne additionally allows for the isolation of a pentacyclic compound lacking the ring enlargement step, which we have proposed as a potential intermediate in the catalytic cycle.
- Carvalho, M. Fernanda N. N.,Herrmann, Rudolf,Wagner, Gabriele
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p. 1230 - 1238
(2017/07/03)
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- (+)-(3-Oxocamphorsulphonyl)oxaziridine as a Highly Stereoselective Reagent for the Oxidation of Sulphides to Chiral Sulphoxides
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The synthesis of the title oxaziridine and its application to the enantio- or diastereo-selective oxidation of sulphides to sulphoxides is described.Enantiomeric excesses up to 66percent are observed, showing the reagent to be superior to most other oxidizing systems.The exceedingly mild reaction conditions (aprotic, neutral) allow the preparation of several chiral α-sulphinyl aldehydes.The properties of these compounds are discussed.
- Glahsl, Gudrun,Herrmann, Rudolf
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p. 1753 - 1758
(2007/10/02)
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