Jadhav Vinod D, Schmidtchen Franz P
Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85747 Garching, Germany.
J Org Chem. 2008 Feb 1;73(3):1077-87. doi: 10.1021/jo7021026. Epub 2007 Dec 28.
A novel synthetic route to the versatile chiral bicyclic guanidinium building block is described making use of l-methionine as a starting material from the natural chiral pool. Furthermore, the synthetic elaboration of this building block is shown in the construction of macrocyclic and open chain hosts, respectively. The host design employs urea functions as the connecting units and supplementary anchor groups for the complexation of anions. The binding studies of these hosts with various chiral and achiral oxoanions are performed by isothermal titration calorimetry. A trend analysis of the binding energetics in an ensemble of structurally similar guests discloses the importance of geometrical confinement of the guest. Association entropy rather than free energy (affinity) is identified as an indicator of structural uniqueness needed to distinguish configurational isomers in the recognition of enantiomeric carboxylates by the chiral guanidinium hosts.
描述了一种新颖的合成路线，以天然手性库中的L-甲硫氨酸为起始原料，合成通用的手性双环胍鎓结构单元。此外，分别展示了该结构单元在大环和开链主体构建中的合成精细过程。主体设计采用脲官能团作为连接单元和用于阴离子络合的辅助锚定基团。通过等温滴定量热法对这些主体与各种手性和非手性含氧阴离子的结合进行了研究。对一组结构相似客体的结合能进行趋势分析，揭示了客体几何限制的重要性。缔合熵而非自由能（亲和力）被确定为手性胍鎓主体识别对映体羧酸盐时区分构型异构体所需结构独特性的指标。
