Chirality Organization of Ferrocenes Bearing Podand Dipeptide Chains: Synthesis and Structural Characterization

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• 作者：Toshiyuki Moriuchi ; Akihiro Nomoto ; Kazuhiro Yoshida ; Akiya Ogawa ; and Toshikazu Hirao
• 刊名：Journal of the American Chemical Society
• 出版年：2001
• 出版时间：January 10, 2001
• 年：2001
• 卷：123
• 期：1
• 页码：68 - 75
• 全文大小：171K
• 年卷期：v.123,no.1(January 10, 2001)
• ISSN：1520-5126

文摘

A variety of ferrocenes bearing podand dipeptide chains have been synthesized to form an orderedstructure in both solid and solution states and have been investigated by ¹H NMR, FT-IR, CD, and X-raycrystallographic analyses. Conformational enantiomerization through chirality organization was achieved bythe intramolecular hydrogen bondings between the podand dipeptide chains. The single-crystal X-ray structuredetermination of the ferrocene 2 bearing the podand dipeptide chains (-D-Ala-D-Pro-OEt) revealed two C₂-symmetric intramolecular hydrogen bondings between CO (Ala) and NH (another Ala) of each podand dipeptidechain to induce the chirality-organized structure. The molecular structures of the ferrocene 1 composed of thepodand L-dipeptide chains (-L-Ala-L-Pro-OEt) and 2 are in a good mirror image relationship, indicating thatthey are conformational enantiomers. An opposite helically ordered molecular arrangement was formed in thecrystal packing of 2 as compared with 1. The ferrocene 2 exhibited induced circular dichroism (CD), whichappeared at the absorbance of the ferrocene moiety. The mirror image of the CD signals between 1 and 2 wasobserved, suggesting that the chirality-organized structure via intramolecular hydrogen bondings is presenteven in solution. The ferrocene 4 bearing the podand dipeptide chains (-Gly-L-Leu-OEt) also showed an orderedstructure in the crystal based on two intramolecular hydrogen bondings between CO (Gly) and NH (anotherGly) of each podand dipeptide chain, together with intermolecular hydrogen bondings between CO adjacentto the ferrocene unit and NH (neighboring Leu) to create the highly organized self-assembly. A differentself-assembly was observed in the crystal of the ferrocene 5 composed of the podand dipeptide chains (-Gly-L-Phe-OEt), wherein each molecule is bonded to two neighboring molecules through two pairs of symmetricalintermolecular hydrogen bonds to form a 14-membered intermolecularly hydrogen-bonded ring. These orderedstructures based on the intramolecular hydrogen bondings in the solution state are also confirmed by ¹H NMRand FT-IR.