Regioselective Diels-Alder reactions of acyl-1,4-benzoquinones 1 with, severally, isoprene, trans-piperylene,1-acetoxy-1,3-butadiene and 1-methoxy-1,3-butadiene gave the corresponding adducts 2 in high yield. Treatment of the adducts 2 with manganese dioxide gave regiospecifically the corresponding 1,4-naphthoquinones 3. In several cases, the adducts of the acetylquinones afforded intermediates...

stepwise and concerted cycloaddition reactions is in mechanistic chemistry. ’ Whereas stepwise processes can often be proven by lack of stereospecifity or by trapping intermediates, 2 it is generally difficult to find unequivocal evidence for concerted processes. Stepwise cycloadditions of neutral components proceed via dipolar or diradical intermediates, which can usually not be generated spec...

Cell envelope fractions from Salmonella can utilize exogenous lipid-linked intermediates for the synthesis of polymeric O-antigen. We describe a method for preparing aqueous suspensions of lipid intermediates and show that freezing and thawing of cell envelope-lipid intermediate mixtures is required for efficient synthesis. The lipid intermediates move freely in the hydrophobic environment of t...

A postcolumn derivatization reversed-phase high-pressure liquid chromatography method has been developed to detect and separate the one-ring open intermediates of dexrazoxane (ICRF-187) in blood plasma. Dexrazoxane is clinically used as a doxorubicin cardioprotective agent and may act by preventing iron-based oxygen-free radical damage through the iron-chelating ability of its one-ring open int...