ORGN 14 |
| Aminophosphonates, the isosteric analogs of corresponding amino acids, are attractive synthetic targets because of their ability to serve as haptens for catalytic antibodies and as other bioactive agents. Although there are numerous methodologies available for the asymmetric synthesis of alpha-aminophosphonates, their beta-analogs received less attention. Therefore, we developed two methods for the stereoselective synthesis of beta-aminophosphonates. The first method involves addition of lithiated phosphonates 1 to activated imines 2 under the catalytic influence of chiral diols such as TADDOL and a polycyclic diol to afford beta-aminophosphonates 3 in high yields and selectivities. The design of the novel polycyclic diol catalyst and scope of the reaction will be discussed. The second method provides beta-nitrophosphonates 6, the immediate precursors to beta-aminophosphonates 3, via phospha-Michael addition of dialkylphosphite 5 to nitroalkenes 4. The Michael addition, performed in the presence of a bifunctional catalyst, (-)-aluminum lithium bis(binaphthoxide), proceeded in high yields and selectivities.
|
|
Asymmetric Reactions and Syntheses
8:00 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. R06, Oral
Division of Organic Chemistry |
