Chem 343 Final - new content

Epimer

carbohydrates: stereoisomers that differ at just one stereocenter

D-Sugar

last chiral carbon is R

Alpha anomer

has OH axial at anomeric carbon

Anomeric Carbon

Carbon on the aldehyde of the original monosaccharide

The anomeric effect

Increased preference for axial anomers with electronegative anomeric carbon

What are the two requirements for the anomeric effect?

atom with lone pairs in the ring and adjacent atom bonded to an electronegative atom

Killani Fischer synthesis

LENGTHENS carbon chain of aldose by 1, new OH can be R or S

Killani-Fischer reagents

1) NaCN, HCl

2) H2, Lindlars cat.

3) H2O, H+

Wohl Degredation

Shortens carbohydrate by 1 carbon

Wohl Degredation reagents

1) NH2OH

2) Ac2O, NaOAc

3) NaOCH3

What happens when you treat a carbohydrate with HNO3?

It oxidizes to put carboxyllic acids on either end of the chain.

How do you assign D or L to amino acids?

Assign priorities assuming R group is third priority, rotation right D, left L

pH<pka

More acidic form (OH, NH3+)

pH > pKa

More basic form (O-, NH2)

pH = pKa

50/50 split

Hell-Volhard-Zelinsky reaction

Creates an amino acid from carboxyllic acid

HVZ reagents

1) PBr3, Br2

2) H2O

3) excess NH3

Amidomalonate synthesis

Creates an amino acid from amidomalonate (1,3 dicarbonyl with amide)

Amidomalonate synthesis reagents

1) CH3O-, CH3OH

2) R-Br

3) H3O+, H2O, heat

Strecker synthesis

Makes an amino acid from an aldehyde

Strecker reagents

1) NH4Cl, NaCN

2) H+, H2O, heat

Can you make a polypeptide with thionyl chloride?

NO, it destroys chirality

Boc Protection

Protects the amino group of a polypeptide by deactivating it

Boc Protection reagents

Boc2O

NEt3

Boc removal reagent

1) TFA

2)NaOH, H2O

How do you activate the carboxyllic acid on an amino acid to form a peptide bond?

DCC, then desired bonding amino acid