反应详情

Synthesis of compounds 16 and 21 are as previously described above. As detailed below, with reference to Scheme 3 and examples 20 and 21, below, the synthesis of compound 26 is described. (+)-pinanediol (1R)-1-acylamino-1-(3-formylphenyl)methylboronates 25, 26 were obtained starting from commercial 2-(3-bromo-phenyl)-[1,3]dioxolane (22a), following the same procedure. Metallation of 22a with buthyllithium at −78° C., followed by reaction with trimethylborate and transesterification with (+)-pinanediol, afforded the desired (+)-pinanediol (3-[1,3]dioxolan-2-yl-phenyl)boronate (+)-23a together with variable amount of (+)-pinanediol (3-dimethoxymethyl)phenylboronate (+)-23b, this latter probably formed by transacetalization with the in situ formed methanol. To avoid this problem, 22a was converted to 22b (88%) and subsequently boronated to (+)-23b (75%).