The peptide bond is between an a amino group and a

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Unformatted text preview: ween an a-amino group and a side-chain carboxylic acid rather than the a-carboxylic acid (b) (6 pts) What type(s) of polymer does glutathione represent? Circle your answer(s): addition polymer heteropolymer biopolymer condensation polymer carbohydrate homopolymer (c) (3 pts) The enzyme g-glutamylcysteine synthetase catalyzes formation of the bond between the side chain of glutamic acid and cysteine. Which of the following pairs of amino acid structures would give the most efficient reaction rate with the natural form of this enzyme? Circle the letter under the box corresponding to the correct set, or, if none are correct, circle the word “NONE”. O O O H2N OH H2N H OH O O H2N OH H2N H H OH H2N H OH SH O B OH H SH O A OH OH H SH O O H2N OH C NONE Comment: Only the naturally-occurring (L) amino acids will react to give the stereochemistry of the glutathione shown above, in which the configurations are also L. MCMP 204 / Exam 2 / Spring 2012 ANSWERS Page 5 *5. (12 points) Use the curved-arrow notation and other reasoning to deduce the structure of the product, which has the formula C6H12O. This product does not react with Br2. Explain your reasoning and show the curved-arrow notation. + HO H3O+ H2O The product has to be cyclic because it has one degree of unsaturation and isn’t an alkene (no reactivity with Br2). The conditions are the same as hydration, so we start the same way: protonation of the double bond to give the more branched (tertiary) carbocation. The nucleophile must be the OH group if we are going to form a cyclic compound. (It has a much greater probability of reacting since it is within the same molecule.) H OH2 CH2 HO + H2O O H3O+ + H3C H CH3 HO H3C O OH2 H3O+ MCMP 204 / Exam 2 / Spring 2012 ANSWERS Page 6 *6. (17 points) a-Promedol is an opiod analgesic (pain killer) discovered in the USSR in the late 1950s. CH3 H R N H3C S (can abbreviate as Ph— in your answers) CH3 S H O C a-Promedol O (a) On the structure above, clearly indicate the R or S stereochemistry of each asymmetric carbon. (b) Draw all four possible chair conformations of a-promedol. (Don’t forget that the a...
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This note was uploaded on 06/18/2012 for the course MCMP 204 taught by Professor Berkstrom during the Spring '08 term at Purdue University-West Lafayette.

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