作者:Jacqueline Marchand-Brynaert、Jean-Christophe Monbaliu
DOI:10.1055/s-0028-1088056
日期:2009.6
Under microwave (MW) heating, 1-diethoxyphosphorylbuta-1,3-diene cycloadds to diethyl, diisopropyl and di-tert-butyl azodicarboxylates leading to the corresponding hetero Diels-Alder (HD-A) cycloadducts in excellent yields. Cycloaddition to the di-tert-butyl derivative is conveniently scaled up using a six-entry parallel synthesis rotor (>10 g scale). B3LYP/6-31G** calculations confirmed the concerted, but highly asynchronous character of this reaction. The di-tert-butyloxycarbonyl cycloadduct is compatible with orthogonal deprotection (i.e., selective N-deprotection without degradation of the phosphonate ester). Thus, reduction and dihydroxylation of the C=C bond of this cycloadduct, followed by TFA deprotection, gave 3-diethoxyphosphorylhexahydro-1,2-pyridazine and 3-diethoxyphosphoryl-4,5-dihydroxyhexahydro-1,2-pyridazine, respectively. This HD-A strategy offers a convenient entry towards phosphonate bioisosters of cyclic α-hydrazino acid and azafagomine derivatives in racemic series.
在微波 (MW) 加热下,1-二乙氧基磷酰基丁-1,3-二烯环加成至偶氮二甲酸二乙酯、二异丙酯和二叔丁酯,以优异的收率生成相应的杂狄尔斯-阿尔德 (HD-A) 环加合物。使用六入口平行合成转子(>10 g规模)可以方便地放大二叔丁基衍生物的环加成反应。 B3LYP/6-31G** 计算证实了该反应的协调但高度异步的特征。二叔丁氧羰基环加合物与正交脱保护相容(即,选择性N-脱保护而不降解膦酸酯)。因此,该环加合物的C=C键的还原和二羟基化,然后TFA脱保护,分别得到3-二乙氧基磷酰基六氢-1,2-哒嗪和3-二乙氧基磷酰基-4,5-二羟基六氢-1,2-哒嗪。这种 HD-A 策略为外消旋系列的环状 α-肼酸和 azafagomine 衍生物的膦酸盐生物电子等排体提供了便捷的途径。