Strategic use of amino acid N-substituents to limit α-carbon-centered radical formation and consequent loss of stereochemical integrity
作者:Anna K. Croft、Christopher J. Easton、Katherine Kociuba、Leo Radom
DOI:10.1016/s0957-4166(03)00542-1
日期:2003.10
amino acid radicals. Optimized structures of glycine derivatives and related substituted methanes, and the corresponding radicals, were determined with B3-LYP/6-31G(d). Single-point RMP2/6-31G(d) calculations on these structures were then used to obtain radical stabilization energies, which were compared with the relative rates of formation of the same or closely similar radicals in reactions with N-bromosuccinimde
从头算开始已经用于研究N-取代基对以α-碳为中心的氨基酸自由基的稳定性的影响。用B3-LYP / 6-31G(d)确定了甘氨酸衍生物和相关取代的甲烷的最佳结构以及相应的基团。然后将这些结构的单点RMP2 / 6-31G(d)计算用于获得自由基稳定能,并将其与在与N-溴代琥珀酰亚胺反应中形成相同或相似自由基的相对速率进行比较。这些研究表明,ñ酰化和磺化降低了α-碳中心自由基的稳定性和易形成性。氟代酰基,氟代烷基磺酰基和亚氨基基团看到了更大的作用。酰亚胺基和氟代烷基磺酰基的作用程度是,使N-邻苯二甲酰基和三氟甲磺酰基保护的氨基酸通过从侧链的氢原子抽象反应,从而避免在手性α-中心反应并保持其立体化学完整性。研究了这些取代基效应的起源。