Diversity-oriented synthesis of peptide-boronic acids by a versatile building-block approach.

A new strategy for the synthesis of peptide-boronic acids (PBAs) is presented. 20 Fmoc-protected natural amino acids with orthogonal side-chain protection were straightforwardly converted into their corresponding boron analogues in three simple steps. Subsequent immobilisation on commercially available 1-glycerol polystyrene resin and on-resin transformations yielded a diversity of sequences in high purity. The strategy eliminates various synthetic obstacles such as multi-step routes, low yields, and inseparable impurities. The described method comprises great potential to be implemented in automated combinatorial approaches by markedly facilitating the access to a variety of PBAs. The coupling of amino acids or other building blocks with α-aminoboronates allows the creation of hybrid molecules with significant potential in various scientific disciplines, such as medicinal chemistry, structural biology, and materials science.

Virtues of Volatility: A Facile Transesterification Approach to Boronic Acids.

Boronic acids are an increasingly important compound class for many applications, including C-C bond formation reactions, medicinal chemistry, and diagnostics. The deprotection of boronic ester intermediates is frequently a problematic and inefficient step in boronic acid syntheses. We describe an approach that highly facilitates this transformation by leveraging the volatility of methylboronic acid and its diol esters. The method is performed under mild conditions, provides high yields, and eliminates cumbersome and problematic purification steps.