I. (42 points) A. Provide the step-wise, curved arrow mechanism for the following (OL 2007, 9, 385). OCH OCH 3

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1 ame Page 1 F FEP1 I. (42 points) A. Provide the step-wise, curved arrow mechanism for the following (L 2007, 9, 85). a l B. Provide the step-wise, curved arrow mechanism for the following (JAS 2002, 124, 11975). ( 2 ) 14 l a ADDITI = tetrahedral int = ELIMIATI = ( 2 ) 14 + ( 2 ) 14 -B ( 2 ) 14 acid catalyst B PRTATI = protonated = = ADDITI = oxonium on R = DEPRTATI = tetrahedral intermediate = PRTATI = oxonium of = ELIMIATI F = protonated = = DEPRTATI = ( 2 ) 14 ( 2 ) 14 ( 2 ) 14 ( 2 ) 14 l ( 2 ) 14 ( 2 ) 14 (2 ) 14 (2 ) 14 ( 2 ) 14 ( 2 ) 14 2 TES: (1) this must be shown as a simple basic mechanism; there is no acid present, so showing the acid-catalyzed mechanism is incorrect (2) the resonance form for the enolate with - is K () if this is shown as an S 2 reaction instead of an acylation, then /9; no credit for the S 1 mechanism (ie, carbocation formation) TES: (1) this must be the acid-catalyzed acylation mechanism; protonation of the = must be first ( 2 ) 14 (2) protonation of the followed by a bunch of S 2 reactions is incorrect B (2 ) 14 (2 ) 14

2 II. (9 points) ame Page 2 F FEP2 A. Isomaltose is a disaccharide found in beer, honey, and other natural products. The IUPA name for isomaltose is!-d-glucopyranosyl-(1->)-"-d-glucopyranose. -2 per error in structure; eg, alpha/beta, stereo, connection TE: can be aworth projections B. omplete the following as required (J 2007, 72, 495). draw one of the product stereoisomers connectivity = 1) 2 MgBr stereochem = 2 2) + protonation ( ) ( ) 2 ( ) ( ) 2 ( ) ( ) connectivity = stereochem = provide oxidation reaction conditons that will not interfere with the ketal PD r py P r VI in acid are not K Swern (just name not K) 1) (l) 2 /( ) 2 S= 2) ( 2 ) full credit writing "Swern" = 2. The following reaction is observed to give a mixture of aldol reaction stereoisomers. Draw one of them (L 2007, 9, 421). connectivity = 4 stereochem = 4 (there are other diastereomers possible) + D. ame this: ( 2 ) 14 ( ) ( 2 ) 14 Bl (catalyst) pentadecyl hexadecanoate ( ) 8-2 per error - pentadecyl, space, hexadecan, oate 7

3 III. (45 points) ame Page F FEP A. Provide a complete, step-wise curved arrow mechanism for the following reaction (L 2007, 9, 5841) S + S ADDITI = 5 zwitterion intermediate = 5 LSURE = 5 S + S( ) 2 TE: this must be the simple basic mechanism; there is no acid present. 15 B. omplete the following reaction scheme as required (J 2007, 72, 47). this must be the neutral atom! no partial 2 Br this undergoes an isomerization via a regioselective ring opening reaction. omplete the following reaction scheme as required. Br wrong regioisomer = 2 points 2 equiv. Li + optional I Li There is no acid here! the no intermediate Li partial must be the anion D. provide the complete IUPA name for this. if it was not the anion, then this S 2 could not take place! the R not good enough nucleophile methyl (E, R)-2-methoxypent--enoate methyl (E, R)-2-methoxy--pentenoate also K if (E),(R)-, or E,R-, order of E and R can be reversed also K if numbered Br TE: the problem says that this is an isomerization! So the formula of the product is the same as the starting material

4 TIS PAGE IS IDEED 40 PITS - the ame IV. (44 points) point values on the cover page for IV/VI were Page 4 F FEP4 switched. GRADED according to these points n April 4, 2007, the US-based company Aminoscience launched a new dipeptide product called "Aminostable," for use in "Aminostable" pharmaceutical products and cell culture 2 media. (a) What is the IUPA name of this dipeptide? alanyl = glutamine = alanylglutamine (b) What is the abbreviation for this dipeptide? AlaGln Ala = Gln = (c) Starting from the amino acid monomers, provide a valid laboratory synthesis for Aminostable. 1) 2) base 2 2 S 4 2 l 2 2 base 2 (d) Using the acid-base properties of the monomers, what is the predicted isoelectric point of Aminostable? 4 pi = ( )/2 (e) What are the two forms of Aminostable in equilibrium at a p 0.5 below the isoelectric point? major form minor form D 2 protect the acid = 5; could be 2 or ( ) protect the amine = 5; could be ( ) (=) coupling with D (abbrev K) = 4 deprotect acid = (could be 2 /Pd- or F 2 with above) deprotect amine = (could be F 2 with above).02 Gln pk 1 = 2.17 Ala pk 2 = ) 2 /Pd- 2) anh Br anh Br R -4 once if switched 2 4 4

5 V. (0 points) omplete the following, as required. (a) L 2007, 9, (b) L 2007, 9, 525 Ts dehydrating conditions 2 1) Tsl/py, PBr, Sl 2, etc Using an R- base 2) LDA is not K - S 2/E2 problem make a leaving group (AT by + 2 = enolate formation = ame Page 5 F FEP5 2 no partial (c) J 2007, 72, 9541 (d) L 2007, 9, excess ( 2 ) 10 Br a ( 2 ) 10 ( 2 ) pts per ether 10 balance the equation connectivity = 2 stereochemistry = 2 methanol = 2 + (e) Gulose is epimeric with glucose at carbons and 4. Draw the modifed Fischer projection for the mixture of anomers from L-gulopyranose. It says modified Fischer projection here, so using a chair drawing or a aworth drawing counts as an error; needs to be the mixture of anomers 2-2 per error

6 ame TIS PAGE IS IDEED 40 PITS - the Page 5 F FEP point values on the cover page for IV/VI were VI. (40 points) switched. GRADED according to these points A. Provide the complete, step-wise curved arrow mechanism for the following reaction You may use B as your generic Bronsted acid.. 2 Ts B PRTATI = 4 oxonium at = 4 ASSISTED IIZATI = 4 ring oxonium = 4 ATTAK BY WATER = 4 oxonium at = 4 DEPRTATI = 4 TE: this is S 1! A correctly drawn S 2 gets 14/28 points. There is a longer S 1 based mech with ring opening that can be correct. WEVER - ring opening S 2 based mechanisms are completely incorrect 28 B. n page 1, you were asked to + ( 2 ) 14 provide the + 2 mechanism for the ( 2 ) 14 acid reaction shown to ( 2 ) 14 ( 2 ) 14 catalyst the right. ow this is interesting: the reaction was done in water... even though neither of the starting materials is water soluble, and the reaction releases water as a by-product. The reason this reaction can occur is because the "acid catalyst" was actually the molecule shown below: S must imply the full micelle! there is a surface monolayer answer that is K Using words, briefly explain why this Using a drawing, illustrate your answer. particular acid catalyst allows the reaction between these two highly water insoluble compounds to react in water. S S S 2 2 S This acid catalyst has the structure of a soap or a detergent. In water, it will form a 2 2 S micelle with a hydrophobic interior. This S ( 2 ) 14 hydrophobic interior provides a place where the highly hydrophobic acid and alcohol ( 2 ) 14 2 molecules can dissolve. 2 The equilibrium between acid and alcohol to give ester plus water is established, and the water is ejected from the hydrophobic interior of the micelle. 2 S S S S 2 2 S 2 PLEASE SEE EXT PAGE FR TE ALTERATIVE RRET ASWERS FR PG VI

7 VI. For part A, there is a much longer yet correct mechanism that involves S 1 and ring opening A. B ALT 2 WEVER: ring opening and S 2 is just incorrect B B. An answer that only shows a layer inside of bulk water is wrong because it ignores the hydrophobic effect favorable here S S S S S 2 ( 2 ) 14 ( 2 ) unfavorable here no credit for answers like this 2 2 owever, you might argue that a surface monolayer forms and the amphopathic molecules all line up and gives an "organic layer" on the top of the water. This sort of argument is K S 2 2 ( 2 ) 14 ( 2 ) 14 ( 2 ) 14 ( 2 ) 14 S S S S S S