Amphoteric α-Boryl Aldehydes

A new class of stable molecules, alpha-boryl aldehydes, has been prepared from oxiranyl N-methyliminodiacetyl boronates by a 1,2-boryl migration with concomitant epoxide scission. A range of boryl imines, alkenes, alcohols, acids, enol ethers, enamides, and other functionalized boronic acid derivatives that are difficult or impossible to prepare using established protocols can be accessed from alpha-boryl aldehydes. The chemoselective transformations of these building blocks, including the facile synthesis of functionalized unnatural amino acids from silyloxy and amido vinyl boronates, attest to the potential of alpha-boryl aldehydes in chemical synthesis.