Page 1 Name:______________________________ CHEM 239A Spring 2002 Exam 3 (100 points). This exam is 5 pages. Please make sure that you have all pages and write your name on each page. Good luck! 1. (6) Name the following amino acids: O O O O O O H2N NH3 OH NH3 O NH3 2. (6) Give common names for the following fatty acids: COOH COOH COOH 3. (3) Show Fisher projections for the following amino acids: L-Methionine D-Alanine 4. (5) Draw a detailed covalent structure for the tripeptide Phe-Gly-Arg. L-Serine Page 2 Name:______________________________ 5. (10) Show an electron-pushing mechanism (using curved arrows) for the following reaction. You do not need to show the mechanism of proton transfer. O + OH NH2 R N C N R O N H O + RHN NHR 6. (10) Porcine dynorphin is a neuropeptide having 17 amino acid residues. Its structure is shown below. Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln a. What is the C-terminus amino acid? b. What fragments would result if dynorphin were cleaved by trypsin? c. What fragments would result if dynorphin were cleaved by chymotrypsin? Page 3 Name:______________________________ 7. (9) Classify the following terpenes (hemiterpene, monoterpene, etc.) and circle the isoprene units. H3C OH COOH H3C 8. (10) Suggest a mechanism, using curved, electron-pushing arrows, by which caryophyllene is transformed into humulene by treatment with acid. H+ 9. (6) Determine the isoelectric point (pI) of the following amino acids, using their pKa values. pKa 6.0 HN NH O pKa 1.8 OH NH3 pKa 9.2 O pKa 10.1 HO pKa 2.2 OH NH3 pKa 9.1 pKa 3.7 HO O O pKa 1.9 OH NH3 pKa 9.6 Page 4 Name:______________________________ 10. (10) Show a step-by step solution phase synthesis of the dipeptide shown below. Show the required reagents and draw the full covalent structures of the intermediates, including the protecting groups. You do not have to show the stereochemistry at the a-carbons. O O + O NH3 H3N Peptide synthesis O O H3N O N H O 11. (10) Provide the missing reagents, starting materials and products in the reactions shown below. Draw all major organic products (containing carbon atoms) for the reactions. You can assume an aqueous work-up after each reaction. NOTE: If no reaction occurs, then write NO REACTION. One or more steps may be required where blank arrows are shown. NH2 O H COOH NH2 O OH OH O O O O O NH2 OH O Br O Page 5 Name:______________________________ 12. (5) Propose a structure for an octapeptide that shows the composition Asp, Gly2, Leu, Phe, Pro2, Val on amino acid analysis. Edman analysis shows a glycine N-terminal group, and carboxypeptidase cleavage produces leucine as the first amino acid to appear. Acidic hydrolysis gives the following fragments: Val-Pro-Leu, Gly, Gly-Asp-Phe-Pro, Phe-Pro-Val 13. (10) Match each of the following terms to a structure from the list below. There is only one correct structure for each term, and structures may be used more than once. Place the letter of the structure for each term in the blank to the left of the corresponding term. O H3C O A. B. O N P O O H N (CH3)16CH3 O O O C. O H D. COOH HO H E. H3C HO CH3 F. CH3 H3C OH COO-Na+ Malonyl ACP (CH3)14CH3 O CH=CH(CH2)12CH3 O (CH3)12CH3 O O O OH HO (CH3)12CH3 (CH3)16CH3 O O O O O O P O (CH3)12CH3 NH3 O OPP SCoA G. H. I. J. a. ______ starting material for fatty acid biosynthesis f. ______ a sphingolipid b. ______ a phosphoglyceride g. ______ a soap c. ______ a prostaglandin h. ______ a cephalin d. ______ monoterpene precursor i. ______ a stereoid e. ______ a triglyceride j. ______ a sesquiterpene