RESUMEN
The first synthesis of sulfonamide and sulfonate analogues of a sulfated carbohydrate in which the ester oxygen of the sulfate is replaced with a CHF or CF2 group is reported. This was accomplished by electrophilic fluorination of the protected sulfonate and sulfonamide precursors. [reaction: see text].
Asunto(s)
Carbohidratos/síntesis química , Fluoruros/síntesis química , Ácidos Sulfúricos/síntesis química , Bromuros/química , Carbohidratos/química , Ésteres/química , Compuestos de Litio/química , Espectroscopía de Resonancia Magnética , Oxígeno/química , Sulfatos/químicaRESUMEN
An efficient three-step synthesis of benzyl 2,3,4-tri-O-benzyl-beta-D-glucopyranoside, a widely used building block in carbohydrate chemistry, is described. The key step is the selective debenzylation-acetylation of perbenzylated beta-glucose using ZnCl2-Ac2O-HOAc. This approach was also used to affect an efficient three-step synthesis of benzyl 2,3,4-tri-O-benzyl-beta-D-mannopyranoside.
Asunto(s)
Glucosa/síntesis química , Glucósidos/síntesis química , Manosa/síntesis química , Manósidos/síntesis química , Glucosa/química , Glucósidos/química , Manosa/química , Manósidos/química , Estructura MolecularRESUMEN
Mandelate racemase catalyzes the interconversion of the enantiomers of mandelic acid. The enzyme binds the intermediate analogues (R)- and (S)-alpha-fluorobenzylphosphonate, and alpha,alpha-difluorobenzylphosphonate with 100-2500 times less affinity than it exhibits for (R,S)-alpha-hydroxybenzylphosphonate at pH 7.5. This apparent low affinity, relative to that of alpha-hydroxybenzylphosphonate, arises from the altered pKa values of the alpha-fluorobenzylphosphonates. For example, (S)-alpha-fluorobenzylphosphonate is bound with the same affinity as the substrate at pH 7.5, but this affinity is increased approximately 6-fold at pH 6.3.
