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Boronic acids are known to bind to active site serines and are part of inhibitors for porcine pancreatic lipase, [2] subtilisin [3] and the protease Kex2. [4] Furthermore, boronic acid derivatives constitute a class of inhibitors for human acyl-protein thioesterase 1 and 2, which are cancer drug targets within the Ras cycle. [5]
Phenylboronic acid or benzeneboronic acid, abbreviated as PhB(OH) 2 where Ph is the phenyl group C 6 H 5 - and B(OH) 2 is a boronic acid containing a phenyl substituent and two hydroxyl groups attached to boron. Phenylboronic acid is a white powder and is commonly used in organic synthesis.
Compounds of the type BR n (OR) 3-n are called borinic esters (n = 2), boronic esters (n = 1), and borates (n = 0). Boronic acids are key to the Suzuki reaction. Trimethyl borate, debatably not an organoboron compound, is an intermediate in sodium borohydride production.
The tert-butyloxycarbonyl protecting group or tert-butoxycarbonyl protecting group [1] (BOC group) is an acid-labile protecting group used in organic synthesis. The BOC group can be added to amines under aqueous conditions using di- tert -butyl dicarbonate in the presence of a base such as sodium hydroxide :
In fact, the addition of acid (H+) or hydroxide (OH-) acts to attenuate protodeboronation by shifting the speciation away from the reactive zwitterion. It is important to note that not all basic heteroaromatic boronic acids are reactive through a zwitterionic intermediate. Scheme for the speciation of 2-pyridine boronic acid in aqueous solution
[5] B2pin2 and B2cat2. The boron atom of a boronic ester or acid is sp 2 hybridized possessing a vacant p orbital, enabling these groups to act as Lewis acids. The C–B bond of boronic acids and esters are slightly longer than typical C–C single bonds with a range of 1.55-1.59 Å.
The mechanism of organotrifluoroborate-based Suzuki-Miyaura coupling reactions has recently been investigated in detail. The organotrifluoroborate hydrolyses to the corresponding boronic acid in situ, so a boronic acid can be used in place of an organotrifluoroborate, as long as it is added slowly and carefully. [7] [8]
The Petasis reaction exhibits high degrees of stereocontrol when a chiral amine or aldehyde is used as a substrate. When certain chiral amines, such as (S)-2-phenylglycinol, are mixed with an α-keto acid and vinyl boronic acid at room temperature, the corresponding allylamine is formed as a single diastereomer.