conformations are observed in the crystal structure of 2, one with both CONH(py) residues pointing with their H-bonding centers NH/N away from the binding site (‘out-out’) and a second (‘in-out’) with one of the two CONH(py) residues pointing towards the binding site (‘in’; Fig. 4). While no H-bonding network propagates throughout the crystal, enantiomers of 2 in the different conformations ‘out-out’ and
所述helicopodand(PM) - 2的制备在photocyclodehydrogenation路线helicenes(以下方案)。在[7]螺旋骨架的末端,该无环受体('podand')具有由两个会聚的N-(
吡啶-2-基)羧酰胺(CONH(py))单元形成的H键识别位点。在[7]螺旋
二乙基-2,17-二
羧酸二
乙酯((PM)-3)的晶体中,2的直接合成前体,具有相同手性的分子形成堆叠,并且具有相反手性的两个堆叠成对互锁。不同对映异构体的苯环之间平均3.82Å的平均面对面芳族接触(图2)。相反,在2的晶体结构中观察到两个构象,一个构象的两个CONH(py)残基都指向其H键中心NH / N远离结合位点('out-out'),而第二个构象('in' -out'),两个CONH(py)残基之一指向结合位点('in';图4)。尽管没有H键网络在整个晶体中传播,但2的对映异构体以不同的构象“向外”