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F.07.210.E2F

# F.07.210.E2F - I(27 points Name Page 1 F.07.210E2 A...

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Name _______________________ Page 1 F.07.210E2 I. (27 points) Malayamycin A, a compound with antifungal and antibacterial activity, was isolated from a soil organism ( JOC 2007 72, 6353). O N H H H H 3 CO H N H N N O NH 2 H O H 2 N HO H 12 A. During the synthesis of Malayamycin A, the following substitution reaction was carried out in two stages. Complete the reaction as required. O O O O O H O Na H Na H + H 2 CH 3 Br B. A certain reaction ( H -> K ) proceeds through intermediate I . Here are some data about the reaction: ! G° from H to K = -2 kcal/mol ! G° from I to K = -10 kcal/mol ! G (activation energy) from K to I = 12 kcal/mol ! G †ˇ (activation energy) from H to I = 16 kcal/mol 2 kcal/mol E progress of reaction Circle all of the tetrahedral stereocenters and clearly assign the stereochemical configuration ( R or S ). (a) (b) (a) Draw an Energy diagram that is consistent with these data. Label I and K , and show the appropriate energy curves. (b) What is the rate determining step for the reverse reaction? H Reaction Coordinate (Energy) Diagram + NaBr 2 2 8 3 R R R R S R or S - BOTH are acceptable answers, the rules for assigning were not covered completely - the actual answer is "S" O O O O O H HO H O O O O O H CH 3 O H 2 points for a correct assignment -2 for identifying a non-stereocenter no partial; complete structure needed I K position I = 2 position K = 2 each curve = 2 I to H needs to state the direction NOTE TO STUDENTS: IF YOU MARKED "S" FOR THIS ONE, IT MIGHT HAVE BEEN MARKED WRONG - WE HAVE GIVEN YOU YOUR POINTS! - DO NOT SUBMIT FOR A REGRADE no partial; complete structure needed

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Name _______________________ Page 2 F.07.210E2 II. ( 20 points) The following electrophilic addition reaction results in a mixture of regioisomers ( P and Q ). CH 3 Cl CH 3 OH catalytic H 2 SO 4 Cl CH 3 O Cl CH 3 O P Q (a) Answer or complete the following: (i) Which of these ( P or Q ) is the major regioisomer? circle one: P Q Provide the structure for the single most important intermediate that is used to explain the regioselectivity, that is, why the major isomer is favored. Show the most significant resonance contributor. (ii) (iii) How many H-NMR signals are expected for Compound Q ?
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F.07.210.E2F - I(27 points Name Page 1 F.07.210E2 A...

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