Abstract:The cathodic reduction of 4-methylcoumarin (1) in acidic methanol/ water in the presence of yohimbine leads to formation of a mixture of the hydrogenation product 4-methyl-3,4-dihydrocoumarin (2), with an enantiomeric excess (ee) of (R)-2 of 0-67Y0, and the hydrodimer 3. The relative yields of 2 and 3 and the ee of 2 depend on a number of experimental parameters such as pH, supporting electrolyte, working potential, and thc concentrations of substrate and yohimbine, as demonstrated by a series of preparative-scale experiments. In addition, a series of voltammetric and kinetic measurements were carried out to investigate the influence of the individual experimental parameters. Three mechanistic possibilities have been examined, and by combination of the analytical data with the results of the preparative experiments, a single model is put forward which is in accord with the available results. The main features of the mechanistic model can be summarized as follows: 1) under acidic conditions (pH 2-3) the electroactive species is a complex between 1 and

A concise route to multigram quantities of the antibacterial diterpene (+)-totarol (1) is reported. (−)-Sclareol (2) was converted to the target compound 1 using either a six-or a seven-step sequence, while only three steps were required to access (+)-totarol (1) starting from (+)-manool (9) or (+)-13-epi-manool (10), respectively. A novel one-pot intramolecular aldol condensation/ α-alkylation protocol served as the key operation for streamlining the syntheses of 1.

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