ChemWiki BioWiki GeoWiki StatWiki PhysWiki MathWiki SolarWiki

Transcription

1 Ashley Robison My Preferences Site Tools FAQ Sign Out If you like us, please share us on social media. The latest UCD Hyperlibrary newsletter is now complete, check it out. ChemWiki BioWiki GeoWiki StatWiki PhysWiki MathWiki SolarWiki Periodic Table of the Elements Reference Tables Physical Constants Units & Conversions Lab Techniques ChemWiki: The Dynamic Chemistry E-textbook > Organic Chemistry > Organic Chemistry With a Biological Emphasis > Chapter 3: Conformations and Stereochemistry > Section 3.P: Problems for Chapter 3 Section 3.P: Problems for Chapter 3 link to Solution Manual P3.1: Below is the structure of sucralose, the artificial sweetener with the brand name Splenda (TM). Give an R or S designation to every stereocenter. P3.2: Below is the structure of the cancer drug Paclitaxel. Give an R or S designation to every stereocenter. P3.3: The four drugs below were featured in a Chemical & Engineering News article (April 16, 2007, p. 42) on new drugs that had been developed in university labs. a) Identify each as chiral or achiral, and identify all stereocenters. Also, state how many possible stereoisomers exist for each structure. 1/7

2 b) Two fluorinated Epivar derivatives (structures A and B below) were also mentioned in this article. What is the relationship between structures A and B?, P3.4: What is the relationship between the two structures below? P3.5: Redraw the following structures in the flat ring, solid/dash wedge convention. P3.6: Below is an experimental drug for Alzheimer's disease that was mentioned in the March 13, 2007 issue of Chemical and Engineering News. a) Label all stereocenters as R or S. b) Draw the enantiomer of the molecule shown. 2/7

3 P3.7: The molecules below are potential new drugs for the treatment of Duchenne muscular dystrophy (molecule A) and skin cancer (molecule B) (Chemical and Engineering News Sept 26, 2005, p. 39). Given the R/S designations, redraw the structure showing the correct stereochemistry. P3.8: Draw the structure of the following molecules: a) (R)-3-methyl-3-hexanol b) (R)-1-chloro-1-phenylethane c) (2R, 3R)-2,3-dihydroxybutanedioic acid (tartaric acid) d) (S)-(E)-4-chloro-3-ethyl-2-pentenoic acid e) (1S, 3R)-1-chloro-3-ethylcyclohexane P3.9: Coelichelin (the structure below to the left) is a natural product from soil bacteria that was identified using a technique known as 'genome mining' (Chemical and Engineering News Sept. 19, 2005, p. 11). What is the relationship between coelichelin and the compound shown below and to the right? P3.10: Designate the following compounds as chiral or achiral P3.11: Identify the relationships between the following pairs of structures (identical, constitutional isomers, enantiomers, diastereomers/not epimers, epimers, or completely different compounds). 3/7

4 P3.12: Identify the relationships between each of the following pairs of pentose sugar molecules (identical, constitutional isomers, enantiomers, diastereomers/not epimers, epimers, or completely different compounds). State how many stereocenters each sugar contains. P3.13: Identify the relationships between each of the following pairs of pentose sugar molecules (identical, constitutional isomers, enantiomers, diastereomers/not epimers, epimers, or completely different compounds). P3.14: A novel and very efficient laboratory synthesis of the natural alkaloid oxomaritidine was described in the March 6, 2006 volume of Chemical and Engineering News (p. 17). The structure is shown below in two dimensions. a) Identify any chiral carbons in the molecule. b) Identify any prochiral hydrogens in the molecule 4/7

5 P3.15: The compound drawn below (not showing stereochemistry) has been identified as a potential anti-inflammatory agent by scientists at Schering-Plough a pharmaceutical company (see Chemical and Engineering News Nov. 28, 2005 p. 29). a) How many stereoisomers are possible for the compound? b) Identify all prochiral hydrogens in the compound. P3.16: Secramine is a synthetic compound that has been shown to interfere with the transport of newly synthesized proteins in the cell (see Chemical and Engineering News Nov. 28, 2005, p. 27). Also drawn below is a (hypothetical) isomer of secramine. a) Identify the relationship between the two isomers: are they consitutional isomers, confomational isomers, enantiomers, or diastereomers? b) Locate a five-membered ring in the secramine structure. P3.17: The natural product bistramide A has been shown to bind to actin, an important structural protein in the cell, and supress cell proliferation (see Chemical and Engineering News Nov. 21, 2005, p. 10). a) Label the alkene functional groups as E, Z, or N (no E/Z designation possible) b) Theoretically, how many stereoisomers are possible for bistramide A? c) What is the relationship between bistramide A and the structure below? 5/7

6 P3.18: Structure A below is that of a newly-developed chiral catalyst (see Chemical and Engineering News Nov. 21, 2005 p. 50). What is the relationship between structures A and B? P3.19: a) Draw Newman projections of the gauche and the anti conformations of 1,2-ethanediol. b) Why might the gauche conformation be expected to be the more stable of the two? c) Do you think that gauche is also the most stable conformation of 1,2-dimethoxyethane? Explain. P3.20:Draw a Newman projection of the highest energy conformation of 2-methylbutane, looking down the C 2 -C 3 bond. P3.21: Draw the lower energy chair conformation of trans-1,2-dimethylcyclohexane. P3.22: Draw the lower energy chair conformation of cis-1-ethyl-2-methylcyclohexane P3.23: Draw the lower-energy chair conformations of cis-1,4-diethylcyclohexane and trans-1,4-diethylcyclohexane. Which is expected to be lowest in energy? P3.24: Draw the lower-energy chair conformations of cis-1,3-diethylcyclohexane and trans-1,3-diethylcyclohexane. Which is expected to be lowest in energy? P3.25: Draw the chair conformation of cis-1,2-dimethylcyclohexane. In this conformation, does the molecule have a mirror plane? Draw a boat conformation of the same molecule that contains a mirror plane, and draw a line to depict that plane (models will help). P3.26: Structure A below is that of artemisinic acid, a synthetic precursor to the anti-malaria drug artemisinin. Identify the relationship (identical, completely different, constitutional isomers, enantiomers, or diastereomers) between the following pairs of structures (it will be very helpful to use models!) a) A and B b) A and C c) B and C d) B and D 6/7

7 P3.27: Redraw the following sugar structures using the zig-zag, solid/dash wedge convention, and assign R/S designations to all stereocenters. Contributors Organic Chemistry With a Biological Emphasis by Tim Soderberg (University of Minnesota, Morris) Copyright 2015 Chemwiki Powered by MindTouch Unless otherwise noted, content in the UC Davis ChemWiki is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License. Permissions beyond the scope of this license may be available at copyright@ucdavis.edu. Questions and concerns can be directed toward Prof. Delmar Larsen (dlarsen@ucdavis.edu), Founder and Director. Terms of Use 7/7