The Half Decent Pharmaceutical Chemistry Blog

Reproterol is a beta-2-agonist used in the treatment of chronic bronchitis and other severe pulmonary diseases.
This molecule is an interesting molecular hybrid of orciprenaline and theophylline: the former is a beta agonist, while the latter increases the concentration of c-AMP either by inhibiting phosphodiesterases or by competing with adenosine. Their combination results in a strong beta-2-selective agonism.

Now, let's take a look at the synthesis. This is a wonderful one and, in my opinion, one of the nicest I've seen so far.

In the beginning, sodium nitrite, with hydrochloric acid, is used to yield an oxime, which is therefore reduced with zinc and hydrochloric acid: one of my favourite ways of doing it!
Before this synthesis, I must confess, I had never seen a formylation: I guess the selectivity is achieved due to the presence of a carbonyl group near one of the two amino functions.

By the way, another amazing step is the hydrogenolysis, which is highly selective for ethers and tertiary amines: here, it removes a protective  benzyl.

A masterpiece!

Of course, if you don't live in Europe, the title will lose all its sense but, come on, use some imagination!
This is the first synthesis here, and I opted for an important drug, Prazosin, mainly used in the treatment of hypertension: an alpha-1-adrenergic antagonist.

This molecule is the lead for other quinazoline derivatives such as doxazosin and cyclazosin.

Here is the synthesis:

This is not totally synthetic, so, if you know a more sophisticated version of this synthesis, please, I'd love to know where I can find it. (I mean, I'm still an undergrad).

For what concerns this synthesis, it's certainly not a complicated one. The very first step involves sodium cyanate and yields a product which can remind of a ketene.
Phosphoroxidchloride is used as chlorinating agent.
I'd like to point out that it's due to thermodynamic reasons that we substitute one Cl only (how lucky, eh?)

The most interesting aspect is the way we yield the furanyl-piperazinyl-methanone. We set pH at 5.5, because the two NH groups in the piperazine have different basicity and this, plus the great reactivity of the furan-2-carbonyl chloride, would lead to double substituted products (hence, a mixture of three products). Thanks to this particular pH, you may say, we protect one of the NH functions and we increase selectivity.