90065-84-2Relevant academic research and scientific papers
Synthesis and properties of pinanediol α-amido boronic esters
Matteson, Donald S.,Jesthi, Pradipta K.,Sadhu, Kizhakethil M.
, p. 1284 - 1288 (2008/10/08)
The use of (+)-pinanediol as the chiral directing group for the synthesis of several α(R)-α-amido boronic esters and acids, which are boronic acid analogues of N-acyl-L-amino acids, has been explored. RBO2Pin (Pin = cis-pinane-2,3-diyl) was homologated to (S)-RCHClBO2Pin, which was converted to (R)-RCH-(NHAc)BO2Pin and, for R = isopropyl, to (R)-RCH(NHCOAc)B(OH)2 by previously reported methods. Where R = isobutyl, methyl, or (benzyloxy)methyl, zinc chloride catalysis was required for the homologation step. Two (S)-acetamido boronic esters (R = isopropyl, isobutyl) were made from (-)-pinanediol. Acylation of the unstable α-amino boronic ester intermediate with carbobenzyloxy chloride was accomplished in the synthesis of PhCH2CH(NHCOOCH2Ph)BO2Pin, but attempted boron trichloride cleavage of the pinanediol boronic ester to the acid also cleaved the benzyloxy group. Hydroboration of allyl halides or allyl benzyl ether with (1,2-phenyldioxy)borane has yielded γ-substituted boronic esters. These were converted to (+)-pinanediol esters and converted by the general route outlined above to α-acetamido δ-substituted boronic esters. (Pinanediyldioxy)borane has been prepared and found to be a sluggish hydroborating agent.
