No abstract

The present work describes a two-step process, namely, silylation with (chloro­methyl)­dimethyl­chloro­silane and desilylation, to address the selectivity problem in the N-methylation of a pyrimidone intermediate toward the synthesis of the raltegravir active pharmaceutical ingredient. The said methodology delivers the desired drug substance in which the O-methylated impurity content is below the detection limit by high-performance liquid chromatography analysis. Moreover, this two-step, one-pot procedure provides an apparent advantage in terms of environmental impact with respect to the optimum approach described in the literature, while it compares equally well in terms of cost and operational simplicity.

The synthesis of (±)-crispine A in 9 steps and 24% overall yield was achieved using a nitrosoalkene hetero-Diels-Alder addition to ethyl vinyl ether as the key step. The synthesis starts from commercial 3,4-dimethoxyphenylacetic acid and uses simple methods, easily accessible materials and inexpensive reagents. An isochroman derivative was unexpectedly formed in an attempted reduction of a dihydro-4H-1,2-oxazine intermediate.

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