Chemistry

Chemistry

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3

FREE RESPONSE SECTION Write your answer in the space provided 1) Draw the mechanisms for each step in the following scheme, draw every arrow and every intermediate.

2A) Predict the structure of the missing molecule for the reversible rearrangement below. Include stereochemistry at any chiral centers or di-substituted double bonds. (5 points)

2B) State which molecule above (A or B) will be favored at equilibrium and why. (3 points)

N NH

NO2

Br O

O

KOH, EtOH, 70 oC

O

O

NO2

NN

i-Pr-NH2, 50 oC O

NO2

NN N H

A B

Boomeranging maEsoaoaEMkMAAiM

••

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4

3) Draw the complete catalytic cycle for the reaction below, including activation of the catalyst if needed. Use a pencil for this… it’s hard to fit it right the first time.

4) Predict the product of this reaction.

Br

CO2Me Pd(PPh3)4

K2CO3, H2O

B OH

OH

CO2Me

N

N O

O

Br

Pd(PPh3)4

Cs2CO3, DMF

goatees

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5

5A) Draw a mechanism for the formation of an iminium ion from the SMs below. There is no other reagent, only an aprotic solvent.

5B) Draw a mechanism for the formation of the endo-substituted product (A) and its conversion to the exo-substituted product (B).

5C) Draw a diagram that accounts for the relative stereochemistry observed in A. 5D) Why is B formed when A is treated with base and a protic solvent (i.e., what’s the driving force)? 5E) React B above with the product from 5A to predict the products in the boxes. DRAW these mechanisms on the next page.

N H

+ H H

O

O

O

H+ NaOMe

MeOH H

O

A B

H

O N H

+ H H

O

B

Product of

assume a small amont of the amine remains

MeMgBr

THF

Teapots

ad

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6

Mechanisms from 5E: 6) Draw a mechanism for the reaction below.

O

Cl

O

OH

SOCl2

To-date

I

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7

7) You have violated quarantine and flown to Australia for some scuba diving and fried baby barramundi! While on the reef, you find a cone snail, and you extract some of its venom. You sneak it back into the US (you are a renegade!), and you set out to determine what the major peptide is in your venom extract, so you can figure out what cone snail species you encountered (you’re clearly a big nerd too). You do a series of experiments because you don’t have a tandem mass spectrometer:

a) You treat with a reducing agent to cleave all disulfides in the peptide. b) You treat with trypsin and observe no change. c) You treat with chymotrypsin and get a heptapeptide and an octapeptide d) You do an Edman degradation of the heptapeptide, and you get a thiohydantoin that is very

polar and reacts with diazomethane to form a methyl ester. DRAW the 2 possible structures of this thiohydantoin here (assume you don’t know the sequence information below yet):

e) You do an Edman degradation of the octapeptide, and you get a thiohydantoin that has a sulfur atom. DRAW the 2 possible structures of this thiohydantoin here (assume you don’t know the sequence information below yet):

f) You consult a recent publication on venom peptides and find the Table below. Which species of cone snail did you encounter? Species:

Name Sequence Organism Diet

LeDr192 ECCEDGWCCTAAPLT C. litteratus vermivorous

!-CnVA ECCHRQLLCCLRFV* C. consors piscivorous

Tx-D0111 QCCWYFDISCCITV C. textile vermivorous

Ca5.1 TCCKFQFLNFCCNE C. caracteristicus vermivorous

* = C-terminal amide, all others C-terminal carboxylic acid

Coated.BA

A

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8

g) You search the protein data bank for this peptide’s name, and you find the ribbon structure to the right. Does your peptide have any of the secondary structures we talked about in class?

h) You decide to make this peptide using solid-phase peptide synthesis.

a. What LINKER will you need to get the correct C-terminal functional group?

b. How many disulfides will be in your final product? 8) Propose a synthesis for each of the molecules below. You may use the starting materials stated and any other reagents you have learned in this course, Orgo I, or even your UG research. Use your own blank pages for your answers to this Q.

A) This molecule is the active ingredient in Clorox wipes!

B) Number your atoms!

C) Use a protected amino acid and things from the toolbox (plus reagents).

N+

Cl- 10

from benzene and 10 Br

H

O

OH

O

O Br

O

H N

O H2N

CH3

CH3

MeO

H

O

MeO

OH

Synthetic toolbox (don’t try to use all of these)

HO

O

NO2

Hoovered

goose

as

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