Stereoselective and also stereospecific condensation at C-4 of flavan-3,4-diols of known absolute configuration with phloroglucinol and resorcinol in acid medium proceeds at ambient temperatures with partial retention of configuration for 2,3-trans-isomers and with inversion for 2,3-cis-analogues. Circular dichroism spectra of the resultant 4-arylflavan-3-ols all exhibit multiple Cotton effects. The
已知绝对构型的黄烷3,4
-二醇与
间苯三酚和
间苯二酚在酸性介质中的C-4立体选择性和立体定向缩合反应在环境温度下进行,部分保留2,3-反式异构体的构型,并转化2 ,3-顺式类似物。所得的4-芳基黄烷-3-醇的圆二色性光谱均表现出多种棉花效应。C-4处的芳基发色团导致的高强度棉花对低波长的影响的迹象几乎总是与该手性中心的2,3-反-3,4-反,2,3-的绝对构型相关反式-3,4-顺式-和2,3-顺式-3,4-反式异构体。