Propranolol

• Propranolol is a non-selective beta-adrenergic receptor blocker (beta-blocker) used primarily to treat cardiovascular conditions such as high blood pressure (hypertension), irregular heartbeats (arrhythmias), and angina (chest pain).
• It is also used to prevent migraines, reduce symptoms of anxiety (especially physical symptoms like rapid heartbeat), and manage certain types of tremors.

Chemical Structure & Formula:

• Consists of a naphthalene (or substituted aromatic) ring linked via an ether bond to a propanolamine side chain.
• Approximate Formula: C₁₆H₂₁NO₂
• Typically administered as a racemic mixture (with the (S)-enantiomer being more potent).
• 

Mechanism of Action:

• Nonselectively blocks both β₁ and β₂ receptors, leading to decreased heart rate, contractility, and myocardial oxygen demand.
• Also reduces renin release from the kidneys, contributing to its antihypertensive effects.

Side Effects:

• Bradycardia and hypotension
• Fatigue and exercise intolerance
• Cold extremities
• Bronchoconstriction (notable in asthmatic patients)

Clinical Uses:

• Used in hypertension, angina, certain arrhythmias, migraine prophylaxis, and essential tremor.

SAR of Propranolol:

1. Aromatic Ring (Naphthalene or substituted phenyl):

   • Lipophilic ring enhances membrane penetration and CNS effects.
   • Substitutions can affect β1 vs. β2 selectivity.

2. Oxymethylene Bridge (–OCH2–):

   • Separates the aromatic ring from ethanolamine moiety; important for β-binding.

3. Propanolamine Side Chain:

   • β-OH group essential for β-receptor interaction.

4. N-substitution:

   • Small alkyl groups like isopropyl: favor β-activity.
   • Larger groups may increase β2 selectivity.

5. Chirality:

   • (S)-enantiomer is more potent in β-blocking activity.

Synthesis of Propranolol:

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