bioex_lect15

bioex_lect15 - potent than the other isomer since the lack...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
MIT OpenCourseWare http://ocw.mit.edu 5.111 Principles of Chemical Science Fall 2008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Restriction of Rotation around Double Bonds See pages 5 and 6 of lecture 15 notes for a description of double bonds using valence bond theory and hybridization. Atoms attached by single bonds can rotate freely around the bond axis. In contrast double bonds prevent rotation around the bond axis, since rotation would break the pi bond (see lecture 15 notes for a discussion of sigma and pi bonds). This means that molecules are made rigid by double bonds, locking a molecule into a specific conformation. For example, cis -butene and trans -butene shown below are two distinct molecules. There is NO rotation around the double bond. Cis and trans -butene are examples of geometric or “cis-trans” isomers. Me C C H H Me H C C Me H Me cis -2-butene trans -2-butene Example from lecture 15 In drugs containing double bonds, one geometric isomer may be significantly more
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: potent than the other isomer, since the lack of rotation around the bond prevents rotational inter-conversion between the two forms. This means that one isomer may be able to achieve the necessary conformation to bind a target molecule (such as an enzyme or receptor), while the other isomer may not be able to bind at all or may be an inferior binding partner. For example, chlorprothixine is a first generation antipsychotic drug that was first used to treat schizophrenia and other disorders in the 1950’s. The drug functions by blocking certain receptors in neurons, which requires binding of the drug to the receptor. Research has shown that cis-chlorprothixene is biologically active, while the trans form is almost completely inactive. In fact, the trans isomer is considered a contaminant in the drug formulation. S Cl H NMe 2 S Cl H Me 2 N cis-chlorprothiexine trans-chlorprothiexine J. Med. Chem. 1993 , 36, 2219-2227....
View Full Document

This note was uploaded on 03/02/2012 for the course CHEM 5111 taught by Professor Vogel during the Fall '08 term at MIT.

Page1 / 2

bioex_lect15 - potent than the other isomer since the lack...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online