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CHEM_302_december2004

CHEM_302_december2004 - FACULTY OF SCIENCE FINAL...

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Unformatted text preview: FACULTY OF SCIENCE FINAL EXAMINATION CHEMISTRY 180-302a (fall) Organic Chemistry Ill Examiners: (3. Just Monday, December 13, 2004 N. Moitessier 69 PM Student name: Student number: This examination consists of two parts. The first part (questions 1-7), worth 70%, should be answered by all. The second part (questions 8-10), worth 0 or 30%, corresponds to the material covered in the first class test. It should only be answered if you wish to improve your mark. Answer the questions in the space provided. No models, calculators etc are allowed Chemistry 302 fall, page 1 1) Provide reagents and mechanisms for the following 3 deprotection steps used in peptide synthesis. i4} (4) H R—NH2 (H30)SC\ Ni “03 H O-n’ R N of ‘R (2)} only reagents O O H : O—l'rhkR O Chemistry 302 fall, page 2 2).Provide the mechanism for the DCC mediated coupling of A and B to give C, and show how N- hydroxybenzotriazole accelerates the reaction (1 D) O 0 COOH ®—\O (913$ «fin R1 A NH + /J\ -“*"-* Wrz< R 2 R1 BNHBoc R c O NHBOC N 000 O (1 “N N—hydroxybenzotriazole N=C=N N OH Chemistry 302 fall, page 3 3. Provide reagents and mechanisms for reactions 3, b and c (10) Ac \OOAC AC ‘OOAC AC ‘OOAC O a O b O c ACO H —-~>- AGO H —"' ACO H H [NH /NH AC/N 0 AC 0 AC 0 _._ PO(OMe)3 \ NHBoc AC‘QOAC \ o A O BocHN COOCHZCHZSiMeg, Ox 0’ ‘0 AcO H NH . /\ Ac” 0 ME3SI NHBOC Chemistry 302 fall, page 4 4.Provide reagents and mechanisms for the following chemical transformation (1 O). H3CO 0 N D N + O HO \ H3CO \ HO H3CO “0 OH OCH3 OH Chemistry 302 fall, page 5 5. Lysine is an important constituent of the aldolase catalyzed condensation of acetaldehyde with glyceraldehyde 3—phosphate to give D~2—deoxyribose 5-phosphate. Provide intermediates and reasonable mechanisms for the transformations.(10) Lys — 2 o 9 A2 ____+. 0 OH ChPO O + k + H/\OPO I T _2 fl OH H CH3 3 ——~——- {\“/““r”‘0P03 a NH2 OH OH OH Chemistry 302 fall, page 6 6. Outline 3 synthesis of stanozolol, starting from androsterone (reagents and intermediates only). (10) OH OH / O a androsterone stanozolol Chemistry 302 fall, page 7 7. Provide mechanisms for the following reactions a,c,d,e used in the synthesis of Viagra.(10) O H 0 CH3 0 CH3 N KI r11 Eto I \ a) (Me0)2802 HO I \( C) HNO3J’HZSO4 HO I \ ’N b) NaOH /N OQN /N O 9H3 N H2N l \ d SOC! N ) 2 02N / e) NH4OH Chemistry 302 fall, page 8 8a) Draw the conformation of a—D-mannopyranose, B—D-galactopyranose, q—Dvglucofuranose, [3—D— mannofuranose and a-D—N—acetylmannosamine {5) i p 8b) Provide a detailed mechanism for the following transformation (5) OH Pin-k O CH30H, H® HO O O H SkH a0 0 H H’ O Chemistry 302 fall, page 9 9.Provide all intermediates and reaction conditions for the synthesis of cellobiose from 1 and 2, and show why the formation of the glycosidic bond is stereospecifio (10). 0A H OH OH H C H “O H H HO 4H H o H HO O W a 0 A00 + O ACO . AoO H —* ,0 go OH O {,0 H H H (O H H H AC] Br H AC 0_CH3 1 2 Cellobiose Chemistry 302 fall, page 10 10. Provide intermediates and mechanisms for the reactions that occur in the following transformation (10) Reaction 1: iodine/aqueous pyridine, or m-chloroperbenzoic acid Reaction 2: aqueous ammonia Reaction 3: mild aqueous acid, followed by neutralization with NaOH 0 o N N (jaw O HO (NfiH DMTrO O N N/ o N NH2 0 o O + side products 0 S = solid support ...
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