Efficient Asymmetric Synthesis of (<i>S</i>)- and (<i>R</i>)-<i>N</i>-Fmoc-<i>S</i>-Trityl-α-methylcysteine Using Camphorsultam as a Chiral Auxiliary
作者:Satendra Singh、Samala J. Rao、Michael W. Pennington
DOI:10.1021/jo049622j
日期:2004.6.1
resulting in the formation of (S)-α-methylcysteine from (1R)-(+)-2,10-camphorsultam and (R)-α-methylcysteine from (1S)-(−)-2,10-camphorsultam after acidic hydrolysis. Subsequent protection of the side chain thiol group with trityl alcohol and α-amine function with Fmoc-OSu furnished fully protected (S)- and (R)-N-Fmoc-S-trityl-α-methylcysteine in overall 20% yield.
将(1 R)-(+)-2,10-和(1 S)-(-)-2,10-樟脑酰胺用2-苯基噻唑啉4-羧酸乙酯酰化,得到(+)-和(-)-2 -苯基噻唑啉基樟脑磺酰胺,其在正丁基锂存在下用MeI立体选择性地烷基化。这些苯基噻唑啉基樟脑苏丹草的烷基化反应是从β面而不是α面发生的,从而导致从(1 R)-(+)-2,10-樟脑苏丹草和(R)-α-形成(S)-α-甲基半胱氨酸酸性水解后的(1 S)-(-)-2,10-樟脑磺胺中的甲基半胱氨酸。Fmoc-OSu提供的三苯甲基醇和α-胺官能团可随后对侧链硫醇基团进行全面保护(S) -和(- [R )- ñ -Fmoc-小号三苯-α甲基半胱氨酸在总产率为20%。