A new route to tricyclane sesquiterpenoids: total synthesis of α-ekasantalic acid.

Chemical manipulation of the cycloadduct of citraconic anhydride and cyclopentadiene enables a new synthetic route to tricyclane sesquiterpenoids. This methodology is applied to the first total synthesis of α-ekasantalic acid.

Control of the stereochemistry of C14 hydroxyl during the total synthesis of withanolide E and physachenolide C.

The stereochemical outcome of the epoxidation of Δ14-15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the ß configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the ß face. The presence of a hydroxyl substituent at C20 does not influence the stereochemical outcome of the epoxidation.

Carbasugar probes to explore the enzyme binding pocket at the anomeric position: application to the design of Golgi mannosidase II inhibitors.

A methodology is described for the highly efficient and divergent synthesis of pseudosugars which allows the stereoselective introduction of polar groups at either the α or the ß pseudoanomeric positions. Using this method, a series of 3-deoxycarbasugar analogues of mannose bearing a pyridyl group are rationally designed, prepared and tested for inhibition of Golgi α-mannosidase II.

Synthesis, chromatographic resolution and chiroptical properties of carboxyibuprofen stereoisomers: major metabolites of ibuprofen in man.

The chromatographic resolution of the four stereoisomers of carboxy-ibuprofen, a major metabolite of ibuprofen in man, was achieved using a Chiralpak AD chiral stationary phase (CSP) (J.T. Baker, Milton, Keynes, UK). The elution order of the stereoisomers was determined to be 2'S,2R;2'R,2R;2'R,2S;2'S,2S by a combination of stereoselective synthesis of diastereoisomeric mixtures and analysis of the two diastereoisomers isolated from human urine following the administration of (S)-ibuprofen. The individual stereoisomers were isolated by semipreparative chiral phase chromatography and characterized by circular dichroism spectroscopy.