Total syntheses of seminolipid and its analogues by using 2,6-bis(trifluoromethyl)phenylboronic acid as protective reagent

Abstract

Total synthesis of seminolipid was accomplished via regioselective protection using 2,6-bis(trifluoromethyl)phenylboronic acid followed by regioselective trichloroethyl-protected sulfation as key steps.

Adjusting the water-sensitivity of sugar/boronate-based organogels

“…Then, we evaluated the influence of phenyl ring substitutions, with the final aim to control the water-sensitivity of such gels. 38,39 However, additional substituents on the phenyl ring also induced a modification of the gelation ability of these molecules. Indeed, the addition of one methyl at the ortho position of phenyl boronate (2b and 4b) increased the MGC of the gelation of toluene to 15 mg mL À1 .…”

“…To reduce even more the water-sensitivity, we envisaged the substitution of the phenyl ring with two o-methyl groups (2d and 4d) or with one trifluoromethyl group (2e and 4e). 38,39 These two modifications dramatically reduced the self-assembling properties of such compounds leading to solutions, even at concentrations higher than 20 mg mL À1 . Therefore, it demonstrated again that slight modulations of the molecular structure induce different or even opposite gelation capacities within this series of compounds.…”

“…Shimada et al took advantage of this feature to envisage them as protecting groups in synthetic schemes. 38,39 In addition, we increased the electron density on the phenyl ring (p-OCH 3 ) which should reduce the electrophilicity of the boron atom and therefore the water-sensitivity of the boronate function.…”

A novel exchange method to access sulfated molecules

“…Organosulfates and sulfamates contain polar functional groups that are important for the study of molecular interactions in the life sciences, such as: neurodegeneration 1 ; plant biology 2 ; neural stem cells 3 ; heparan binding 4 ; and viral infection 5 . Recent total syntheses including 11-saxitoxinethanoic acid 6 , various saccharide assemblies 7 – 10 , and seminolipid 11 have all relied on the incorporation of a highly polar organosulfate motif. Importantly, the first in class organosulfate containing antibiotic, Avibactam 12 , has led to the discovery of other novel β-lactamase inhibitors 13 , 14 .…”

Boronic Acid-Catalyzed Regioselective Koenigs–Knorr-Type Glycosylation

“…The method widely used to realize the construction of a new glycosidic linkage, which forms the basis of synthetic carbohydrate chemistry, is regioselective glycosylation triggered by the formation of a nucleophilic tin acetal using a stoichiometric amount of n Bu 2 SnO. − The development of regioselective glycosylation using less toxic organoboron compounds began in the early 2000s. The Boons, Crich, Kaji, Madsen, and Taylor groups independently reported the regioselective masking , of hydroxy groups on glycosyl acceptors using polymer-supported boronic acid or aromatic boronic acid reagents, and the subsequent regioselective glycosylation of a free hydroxy group. Complementing the methodology based on the deactivation of glycosyl acceptors through the formation of a tricoordinated boronic ester intermediate, regioselective glycosylations based on the activation of the glycosyl acceptor via a tetracoordinated boronate intermediate have also been reported.…”