A New Helicopodand: Molecular Recognition of Dicarboxylic Acids with High Diastereoselectivity
A New Helicopodand: Molecular Recognition of Dicarboxylic Acids with High Diastereoselectivity
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一种新的螺旋足动物：具有高非对映选择性的二羧酸分子识别
DOI：
10.1002/hlca.19930760803
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发表时间：
1993
影响因子：
1.8
通讯作者：
C. Knobler
中科院分区：
文献类型：
--
作者：
L. Owens;C. Thilgen;F. Diederich;C. Knobler
螺旋足 (PM)-2 是按照光环脱氢路线制备螺旋烯的（方案）。在[7]螺旋烯主链的末端，这种无环受体（‘podand’）具有由两个会聚的 N-(吡啶-2-基)甲酰胺 (CONH(py)) 单元形成的氢键识别位点。在[7]螺烯-2,17-二甲酸二乙酯（(PM)-3）（2的直接合成前体）的晶体中，相同手性的分子形成堆叠，并且两个相反手性的分子堆叠成一对，不同对映体的苯环之间的平均面对面芳香接触为3.82 A（图2）。相比之下，在2的晶体结构中观察到两种构象，一种是两个CONH(py)残基都指向其氢键NH/N远离结合位点的构象(“out-out”)，另一种(“in-out”)，两个CONH(py)残基之一指向结合位点(“in”；图4)。虽然没有氢键网络在整个晶体中传播，但不同构象“out-out”和“in-out”的 2 对映体形成氢键对，这些氢键对通过与一个 CHCl3 分子的氢键进一步稳定。在生产性的“in-in”构象中，2 与 CHCl3 中的 α,ω-二羧酸形成稳定的 1:1 络合物，并且对于仅在双键处的 (E)/(Z) 构型不同的两种底物，测量了 Δ(ΔG°) = 1.4 kcal mol−1 络合中的非对映选择性（参见表 2）。综合力场分子模型研究表明，只有 (E)-衍生物具有正确的几何结构，可在其两个 COOH 残基和 2 中的两个 CONH(py) 基团之间形成双位四重氢键相互作用（图 5）。使用N,N'-双[(苄氧基)羰基]-L-胱氨酸，观察到与(PM)-2形成非对映异构体复合物(图7)。
The helicopodand (PM)-2 is prepared following the photocyclodehydrogenation route to helicenes (Scheme). At the ends of a [7]helicene backbone, this acyclic receptor (‘podand’) possesses a H-bonding recognition site shaped by two convergent N-(pyridin-2-yl)carboxamide (CONH(py)) units. In the crystal of diethyl [7]helicene-2,17-dicarboxylate ((PM)-3), a direct synthetic precursor of 2, molecules of the same chirality form stacks, and two stacks of opposite chirality are interlocked in a pair having average face-to-face aromatic contacts of 3.82 A between benzene rings of different enantiomers (Fig. 2). In contrast, two 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 ‘in-out’ form H-bonded pairs that are further stabilized by a H-bond to one molecule of CHCl3. In the productive ‘in-in’ conformation, 2 forms stable 1:1 complexes with α,ω-dicarboxylic acids in CHCl3, and a diastereoselectivity in complexation of Δ(ΔG°) = 1.4 kcal mol−1 is measured for two substrates differing only in the (E)/(Z)-configuration at their double bond (see Table 2). A comprehensive force-field molecular-modeling study suggests that only the (E)-derivative possesses the correct geometry for a ditopic four-fold H-bonding interaction between its two COOH residues and the two CONH(py) groups in 2 (Fig. 5). With N,N′-bis [(benzyloxy)carbonyl]-L-cystine, the formation of diastereoisomeric complexes with (PM)-2 is observed (Fig. 7).
影响因子：
15
作者：
Yasutaka Tanaka;Y. Kato;Y. Aoyama
通讯作者：
Yasutaka Tanaka;Y. Kato;Y. Aoyama
影响因子：
3
作者：
WEINER, SJ;KOLLMAN, PA;CASE, DA
通讯作者：
CASE, DA