CaltechTHESIS
  A Caltech Library Service

Studies in Molecular Recognition: Hydrophobic Binding of Water-Soluble Guests by High Symmetry, Chiral Hosts

Citation

Shepodd, Timothy Jon (1988) Studies in Molecular Recognition: Hydrophobic Binding of Water-Soluble Guests by High Symmetry, Chiral Hosts. Dissertation (Ph.D.), California Institute of Technology. https://resolver.caltech.edu/CaltechTHESIS:03072013-150951099

Abstract

A new class of high-symmetry, water-soluble receptors has been synthesized. The enantiomerically pure hosts are D₂-symmetric and are synthesized in 8 steps with an overall yield of 5-10%. An asymmetric Diels-Alder reaction between di-(+)-menthyl fumarate and 2,6-di-t-butyldimethylsiloxyanthracene leads to two diastereomeric Diels-Alder adducts that are elaborated to the key intermediates: (+)- and (-)-2,6-dihydroxy-11,12-dicarbomethoxy-9,10-ethenoanthracene. A number of hosts are synthesized from these intermediates when they are connected by variable linker units. These hosts possess chiral cavities (receptor sites) surrounded by an array of substituted aromatic rings.

The ability of these hosts to complex water-soluble guests with different sizes, shapes, and degrees of preorganization has been quantified by NMR. The electron-rich hosts have a general affinity for electron-deficient guests. Hosts P and M show a moderate hydrophobic-type attraction towards a variety of aromatic and aliphatic guests (3-4 kcal/mol). Host P shows an added attraction towards trimethylammonium (TMA) substituted guests. In almost all cases studied, NMR-shift patterns indicate that when the hostguest complex forms, the polar TMA group lies deepest within the electron-rich, yet hydrophobic, receptor.

Hosts P and M have a strong attraction towards adamantyltrimethylammonium iodide (ATMA). PR and PS have binding viaffinities of 6.6 ± 0.2 kcal/mol with ATMA and bind the guest, encapsulated within the receptor site, in one guest orientation. MR and MS have binding affinities of 5.5 ± 0.2 kcal/mol with ATMA and bind the guest in a non-specific fashion, yet they demonstrate a preferred attraction towards the TMA group of the guest.

Aromatic-linked hosts PR, PS, MR and MS show an enhanced ion-dipole attraction towards charged quinolinium-type, flat aromatic guests as compared to neutral ones (P ≈ 1 kcal/mol and M ≈ 2 kcal/mol). Host C, with aliphatic linkers, does not experience an enhanced attraction to the charged flat guests.

Hosts PR and PS demonstrate enantioselective binding with certain guests. For one case, a simple model for the cause of the enantioselectivity is presented.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Dougherty, Dennis A.
Thesis Committee:
  • Dervan, Peter B. (chair)
  • Dougherty, Dennis A.
  • Baldeschwieler, John D.
  • Myers, Andrew G.
Defense Date:4 February 1988
Additional Information:Title in 1988 commencement program -- Studies in Molecular Recognition: Hydrophobic Binding of Water-Soluble Guests by High-Symmetry, Chiral Hosts -- varies slightly from title in thesis file (PDF).
Funders:
Funding AgencyGrant Number
NIHUNSPECIFIED
W. R. Grace FellowshipUNSPECIFIED
Howard Scrap Metal CompanyUNSPECIFIED
Record Number:CaltechTHESIS:03072013-150951099
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:03072013-150951099
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7504
Collection:CaltechTHESIS
Deposited By: Dan Anguka
Deposited On:07 Mar 2013 23:54
Last Modified:02 Dec 2020 01:50

Thesis Files

[img]
Preview
PDF - Final Version
See Usage Policy.

23MB

Repository Staff Only: item control page