Methyl 5-hydroxy-beta-orsellinate

The clinically used DNA-alkylating drug streptozotocin (STZ) was investigated using a simple work-up as an O-methylating agent to transform various carboxylic acids, sulfonic acids and phosphorous acids into corresponding methyl esters, and did so with yields of up to 97% in 4 h at room temperature. Good substrate tolerance was observed, and benefited from the mild conditions and compatibility of the reaction with water.

Mercury (Hg) methylation, methylmercury (MeHg) demethylation, and inorganic redox transformations of Hg are microbe-mediating processes that determine the fate and cycling of Hg and MeHg in many environments, and by doing so influence the health of humans and wild life. The discovery of the Hg methylation genes, hgcAB, in the last decade together with advances in high throughput and genome sequencing methods, have resulted in an expanded appreciation of the diversity of Hg methylating microbes. This review aims to describe experimentally confirmed and recently discovered hgcAB gene-carrying Hg methylating microbes; phylogenetic and taxonomic analyses are presented. In addition, the current knowledge on transformation mechanisms, the organisms that carry them out, and the impact of environmental parameters on Hg methylation, MeHg demethylation, and inorganic Hg reduction and oxidation is summarized. This knowledge provides a foundation for future action toward mitigating the impact of environmental Hg pollution.

Direct reductive N-methylation of inexpensive and readily available nitro compounds as raw material feedstocks is more attractive and straightforward compared with conventional N-methylation of amines to prepare biologically and pharmaceutically important N-methylated amine derivatives. This strategy for synthesis of N-methylamines avoids prepreparation of NH-free amines and therefore significantly shortens the separation and purification steps. In recent years, numerous methylating agents and catalytic systems have been reported for this appealing transformation. Thus, it is an appropriate time to summarize such advances. This review elaborates on the most important discoveries and advances in this research arena, with special emphasis on the mechanistic aspect of reactions that may provide new insights into catalyst improvement.