Synthesis of trioxatricornan and derivatives. Useful keystones for the construction of rigid molecular cavities
作者:Michael Lofthagen、Russell VernonClark、Kim K. Baldridge、Jay S. Siegel
DOI:10.1021/jo00027a015
日期:1992.1
The synthesis of a new class of organic keystones for the development of macrocage structures is presented. These represent some of the most versatile building blocks for macrocage construction. The keystone structure developed herein can be interpreted as either a centrally alkylated [cd,mn]dibenzopyrene or a tris ortho-bridged triphenylmethane. We call this basic skeleton tricornan. Routes into both chiral (C3 and C1 symmetry) and achiral (C3-upsilon symmetry) derivatives are reported. The synthesis of derivatives of the trioxatricornan keystone, leading to two macrocage structures, is presented. The X-ray structures of cent-methyltrioxatricornan 7 and 2,6,10-tris(dimethylamino)-cent-methyltrioxatricornan (20) are discussed and compared to that of 1,1,1-triphenylethane. Empirical force field and AM1 calculations are compared to the X-ray structures and discussed. A general discussion on the keystone analogy is presented.
Induced Folding by Chiral Nonplanar Aromatics
作者:Sri Kamesh Narasimhan、Deborah J. Kerwood、Lei Wu、Jun Li、Rosina Lombardi、Teresa B. Freedman、Yan-Yeung Luk
DOI:10.1021/jo9013047
日期:2009.9.18
motif based on a C3-symmetric bowl-shaped core, on which three substituted amino acids on the periphery adopt either a folded or a spread-out conformation. This class of chiralfolded structures is achieved by controlling the reactivity of the stereogenic protons on the nonplanararomatic rings of trioxatricornan to afford predominantly C3-symmetric isomers. Bromination of trioxatricornan afforded a C1-symmetric