Hypertensives Flashcards
ACE is what kind of peptidase?
Non selective
Where does ACE cleave?
On the last two amino acids from many peptides
Where does ACE not cleave?
On peptide in which the second last amino acid is PROLINE
How many amino acid does angiotensin 1 have?
10 amino acids
How many amino acids does Angiotensin 2 have?
8 amino acids, the second last amino acid is proline
what is the name of the snake where the scientists got the venom from?
Bothrops Jararaca
What does the venom do.?
Decrease BP, Can cause death
It inhibits ACE
What is the name of the peptide isolated from the venom?
Teprotide
Why is teprotide not good?
Because it is not orally active
Second amino acid is proline
How is ACE and carboxypeptidase similar?
They both need Zn2+ for activity, both are peptides
What is the inhibitor of carboxypeptidase A?
D-2-benzylsuccinic acid
How to make D-2-methylsuccinic proline
from D-2-benzylsuccinic acid?
Add proline group to make ACE recognise it
π succinyl-proline
increase the chain length by adding a methyl like the dipeptides
π D-2-methylsuccinic proline
How to make captopril
add THIOL GROUP to D-2-methyl succinic proline
Change COOH to -SH which can act as Zn2+ ligand,
Interacting with positive
CAPTOPRIL SARs
Methyl : increased potency 20x
Thiol: increase potency x1000
Any possible modification to captopril
Addition of S in 5-ring π thioproline
Addition of benzene to the 5-ring (benzofusion) π increase potency 3-7x
When can captopril be inactive?
When benzene ring is added too close to the COOH
π steric hindrance
Some limitation of captopril caused by SH (thiol)
Rash, change/loss of taste
What is the ACEI without the thiol group
Enalapril
How to make enalaprilat from D-2-methylsuccinyl pro?
Add amine (NH) to make it more like a peptide Add silicon/ benzene to make it more lipophilic
Is enalaprilat a good ACEI?
No, it is very polar due to too many charges (too much ionisation by 2 x COOH and NH)
ππadd an ester to the top COOH. And make it enalapril (prodrug)
Enalapril and enalaprilat ionisation difference
Enalapril - pKa (NH) ~5.5
Less ionised at physiological pH, non polar, orally active
Enalaprilat - pKa (NH) ~7.6
More ionised, very polar, orally inactive
Enalapril SARS
S1- amine ring and COOH (needed for activity)
S2 - methyl group
S3 - benzene ring
When does enalapril lose activity?
S1 When proline is removed When COOH is converted to amide S3 When branching on a-carbon (2 carbons away from benzene) When addition of acidic side chain S2 When any carbon branching (steric hindrance) When addition of acidic side chain
How to make indolapril?
From enalapril, on s1, add 6-ring onto the amine ring (retained activity)
Any fine modification on captopril
On s3- modification of aliphatic and aromatic rings
On s2- many side chains
All retain activity
How to make Lisinopril
S2= (CH2)4 NH2
Do not need to convert to ester
Because lisinopril is a Di-zwitterion in the duodenum pH
It forms ion pairs and can cross membrane together
π orally active
What is the first ARB made from?
Takes a lead
based on βimidazole-Ββ5-Ββacetic acid analoguesβ β patent ο¬led
What did DuPont Merck do to make a different ARB?
Tried to make a new one based on peptide inhibitor but failed
Looked at what the takeda lead contained to mimic ang2
and what the takeda lead was missing
DEVELOPED LOSARTAN
What does takeda lead have that mimic the ang 2?
1) β― C-Ββterminus carboxylate ion (on the right end)
2) β― Imidazole ring (between carboxylate ion and butyl group, at the bottom)
3) β― n-Ββbutyl group of S-Ββ8038 similar to isoleucine side chain of Ang II (in the middle on top)
What was takeda lead missing?
Acidic side chain on the N terminus
Good interaction on the C terminus but barely any interaction on the N
Big breakthrough in developing ARB from takeda lead
Addition of acidic group (COOH) on the benzene ring
How to make losartan?
Through further modification to takeda lead including addition of acidic group
ππ tetrazole group on the benzene ring (mimicking the COOH group, the negative charge)
One example of losartan analogues
And what does it need?
Valsartan
It needs ester groups (pro drugs need to be hydrolysed to become active)
Other improvements on takeda lead
Instead of focusing on the missing acidic group on n terminus,
Focus on mimicking the c terminus as much as possible
πEprosartan
Activation of beta-1 adrenergic receptor leads toβ¦
Increase rate and force of cardiac contractions
Increase blood pressure
Activation of beta-2 adrenergic receptors leads toβ¦
Bronchodilation
What are the two types of non-selective beta adrenergic receptor blockers?
Arylethanolamine type e.g. Sotalol
Aryloxypropanolamine type e.g. Propranolol
What is the general rule of selective beta-1 adrenergic receptor blocker?
4-(para) substituted phenoxypropanolamines
If 3-substituted, it is non-selective
What stops the alpha-activity of other beta-blockers?
What is lacked in the mixed alpha/beta adrenergic blockers?
N substituents
What are the examples of mixed alpha and beta blockers
Carvedilol and labetalol
What are the examples of selective beta 1 receptor blockers?
Atenolol, metoprolol
What are the examples of non selective betablockers
Sotalol, propranolol
What happens if you activate alpha receptor
Vasoconstriction
What is the non selective AGENT of alpha blocker?
Phenoxybenzamine
What is the stable salt form of phenoxybenzamine?
Aziridinium ion (high reactive in water) It reacts with nucleophile group (S,N,O) of an amino acid on an alpha receptor.
What is the name of the receptor when the drug is covalently bonded to the alpha receptor?
Alkylated receptor
What is the duration of action of phenoxybenzamine?
Very long acting
Because the drug is stuck to the receptor and the only way to get rid of this effect is to make a new receptor (as the receptor is alkylated)
What is phenoxybenzamine used for?
To relieve symptoms of some adrenal tumours that secrete large amounts of A and NA
What is the classic a1 selective antagonist?
And what aromatic ring does it contain?
Prazosin
Quinozoline (two 6-rings together), aliphatic 6-ring, furan ring (5-ring with oxygen)
How do you increase duration of action in a1 selective antagonist?
Reduce the furan ring (From double bond to single bond)
Centrally acting agents are what type of receptor agonist?
A2 adrenergic receptor
What happens if you activate A2 receptor?
Decrease in BP β> antihypertensive
Where else can a1 agonist be used for?
Nasal decongestant
What are examples of centrally acting agent? - a2 agonist
Clonidine (classic), guanabenz, a-methyl norepinephrine (prodrug is methyldopa)
What is important in a way clonidine acts?
Conformation and ring orientation
Does methyldopa cross BBB
Yes
What do CCB target in the cells?
L- type calcium channels
What are the chemical classes in CCB?
Dihydropyridine eg. Amlodipine
Phenylalkyamines eg. Verapamil (OFTEN SYMMETRICAL)
Benzothiazipines eg. Diltiazem (Sulfur in the ring)
Diaminopropanol eg. Bepridil (rare)
What is special about dihydropyridines?
Subtle changes in structure can change properties
You can make it a calcium channel activator
(Swapping CO2CH3 in isradipine to NO2)
Dihydropyridines SARS
Substituted phenyl ring at the C4 position optimises activity
Ortho or meta substituents increase activity
PARA or None substituents decrease activity