| Budget Amount *help |
¥15,500,000 (Direct Cost: ¥15,500,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2003: ¥13,300,000 (Direct Cost: ¥13,300,000)
|
|---|
| Research Abstract |
Increasing environmental awareness makes it necessary to develop sustainable synthesis of amino acids without the use of highly toxic agents such as cyanides. In this context, reductive amination of keto acids has merited special attention, because it is a close laboratory analogy of a pathway by which amino acids are chemoselectively biosynthesized with aqueous ammonia that is an essential amine source in natural system. In nonenzymatic synthesis of amino acids, however, catalytic reductive amination has so far been carried out using amine sources other than ammonia in organic solvents. Thus, catalytic reductive amination of keto acids with aqueous ammonia has yet to be achieved. The difficulty of such reactions mainly arises from the use of water as a reaction media. The aqueous media must be acidic enough for the carbonyl group of keto acids to be protonated. However, the presence of proton causes not only the decomposition of a hydride species, which would act as a catalyst, but al
… More
so formation of the hydroxy carboxylic acids as a by-product by the competitive transfer hydrogenation of keto acids. We have investigated highly chemoselective synthesis of amino acids by reductive amination of commercially available keto acids, catalyzed by acid-stable mononuclear hydride complexes with aqueous ammonia and HCOOY (Y=Na or H) in water. The reductive amination is applicable to the highly chemoselective synthesis of all three major types of amino acids with nonpolar, uncharged polar, and charged polar substituents by controlling pH. This is the first example of highly chemoselective nonenzymatic synthesis of amino acid by catalytic reductive amination of keto acids with aqueous ammonia in water. pH-dependent (15)N- and D-double-labeling can also be readily accomplished by using (15)N-ammonia and DCOONa, which are ideal amine and hydride ion sources, respectively. Thus, the highly chemoselective synthesis of amino acids with negligible formation of hydroxy carboxylic acids has been made possible by using acid-stable hydride complexes under the optimized pH conditions in water. Less
|
