Structure of a reaction intermediate mimic in t6A biosynthesis bound in the active site of the TsaBD heterodimer from Escherichia coli.

The tRNA modification N6-threonylcarbamoyladenosine (t6A) is universally conserved in all organisms. In bacteria, the biosynthesis of t6A requires four proteins (TsaBCDE) that catalyze the formation of t6A via the unstable intermediate l-threonylcarbamoyl-adenylate (TC-AMP). While the formation and stability of this intermediate has been studied in detail, the mechanism of its transfer to A37 in tRNA is poorly understood.

Efficient preparation of 2,4-diaminopyrimidine nucleosides: total synthesis of lysidine and agmatidine.

An efficient route for the synthesis of 2,4-diaminopyrimidine ribosides from cytidine is described consisting of six steps with overall yields >50% and only one chromatographic step. The key amine addition step utilizes LiCl and 1,8-diazabicyclo[5.4.