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PHA111 > Peptide Synthesis > Flashcards

Peptide Synthesis Flashcards

1
Q

What are natural peptides commonly used as?

A
  • signalling molecules i.e. hormones, neurotransmitters

- substrates

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2
Q

What is a peptidomimetic?

A

A peptidomimetic is a small protein-like chain designed to mimic a peptide

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3
Q

Give examples of peptides & peptidomimetics in clinical use

A
  • insulin

- interferons

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4
Q

Why is peptide synthesis important?

A

For drug manufacture and discovery

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5
Q

What are the 2 amino protecting groups?

A
  • amides

- carbamates

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6
Q

How does N protection work?

A
  • aims to make N non-nucleophilic

- removes lone pair availability

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7
Q

What is the most common N-protecting group?

A

carbamate

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8
Q

What depends on choice of carbamate?

A

functional group sensitivity in target molecule

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9
Q

Name the 3 types of sensitivity on target molecules

A
  • acid sensitive (tBoc)
  • reduction sensitive (Cbz)
  • base sensitive (Fmoc)
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10
Q

What is the most common reagent used in tBoc protection?

A

Boc anhydride

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11
Q

What is used in tBoc de-protection?

A

TFA - trifluoroacetic acid

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12
Q

What is the source of Cbz protection?

A

benzyoxycarbonyl chloride

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13
Q

What 3 amino acids is Cbz protection unsuitable for?

A

Cys
Met
Lys

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14
Q

In Cbz proetction is R1=H, what is the product?

A

Cbz-Gly

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15
Q

How does Cbz de-protect?

A

Hydrogenation

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16
Q

In Fmoc protection why is succinimidyl ester often used?

A

Good leaving group

17
Q

In Fmoc protection is R1=H, what is the product?

A

Fmoc-Gly

18
Q

How does Fmoc de-protect?

A

With a mild base

19
Q

Why does Fmoc not de-protect with a strong base?

A

Strong bases cause racemisation of amino acids - so we end up with a 1:1 mixture of D and L isomers

20
Q

What happens when we end up with 1:1 D +L isomers?

A

We get peptides with non-natural stereoisomers that are usually inactive

21
Q

Name a carboxyl protecting group

A

Esters

22
Q

Methyl and ethyl esters hydrolyse with ______

A

hydroxide

23
Q

tertiarybutyl hydrolyses with ___

A

TFA

24
Q

Benzyl hydrolyses with ________

A

hydrogenate

25
Q

Solid Phase Peptide Synthesis (SPPS) is a multistep solution synthesis that gives high/low overall product yields

A

low

26
Q

What is SPPS performed on?

A

insoluble polymer bead

27
Q

Describe the process of SPPS

A
  • Add C-terminal amino acid to bead
  • deprotect N-terminus
  • add activated ester of 2nd amino acid
  • deprotect N-terminus of dipeptide
  • add activated ester of 3rd amino acid
  • deprotect new N-terminus
  • cleave peptide from resin
28
Q

What are the advantages of SPPS?

A
  • automation
  • rapid reliable
  • easy purification
  • cheap
  • many different applications
29
Q

What are the reactive side chains?

A
  • N-containing
  • Carboxylate
  • Alcohol
  • Thiol
30
Q

What is the orthogonal protection strategy of reactive side chains?

A
  • can use same protecting groups considered but not the same group used to protect the end of the chain
31
Q

If tBoc/Fmoc were used on the N-terminus why cant they be used on side chains?

Why is this bad?

A

it will de-protect at same time as N-terminus

  • significant by-products
  • harmful/inactive if administered
32
Q

Peptide coupling is carried out using _______

A

carbodiimides

33
Q

Why is Cbz rarely used as an N protecting agent of terminal amino acid?

A

requires hydrogenation

  • incompatible with industrial scale + resin issues
34
Q 
Which reagent(s) would be most suitable for removing a Cbz-protecting group?
	A	TFA
	B	HF
	C	DCC
	D	H2 / Pd-C
	E	Morpholine
A

D H2 / Pd-C

35
Q 
Which reagent(s) would be most suitable for coupling two amino acids together.
	A	TFA
	B	HF
	C	DCC
	D	H2 / Pd-C
	E	Morpholine
A

C DCC

36
Q 
Which reagent(s) would be most suitable for removing a peptide from Merrifield resin?
	A	TFA
	B	HF
	C	DCC
	D	H2 / Pd-C
	E	Morpholine
A

B HF

PHA111 (23 decks)

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