Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Org Lett. 2010 May 7;12(9):1924-7. doi: 10.1021/ol100467t.
Oximes and alpha-ketoacids undergo an unexpectedly facile and chemoselective annulation to afford 2,5-dihydrooxazole 3-oxides. The resulting cyclic nitrones serve as chemically and configurationally stable masked alpha-ketoacids that can be easily elaborated and manipulated. Deprotection is achieved by mild reduction with zinc metal and hydrolysis. This methodology allows for the protection, elaboration, and deprotection of enantiopure peptide derived alpha-ketoacids, which are the key starting materials for the chemoselective ketoacid-hydroxylamine peptide ligation.
肟和α-酮酸发生出乎意料的容易和选择性的环化反应,生成 2,5-二氢恶唑 3-氧化物。所得的环状亚硝酮作为化学和构型稳定的掩蔽α-酮酸,可以很容易地进行修饰和操作。脱保护通过温和的锌金属还原和水解来实现。这种方法允许保护、修饰和脱保护手性纯肽衍生的α-酮酸,它们是化学选择性酮酸-羟胺肽连接的关键起始材料。