Advances in the synthesis of 7-(3-cyclopentyloxy-4-methoxyphenyl)-hexahydro-3H-pyrrolizin-3-one (Pyrromilast)–a promising agent for treatment of chronic obstructive pulmonary disease

Catalytic Reductive Recyclization of Functionalized Isoxazoline N-Oxides to Pyrrolizidine-3-ones

Pyrrolizidine is among the saturated N-heterocyclic scaffolds most frequently found in natural products and pharmaceutically relevant substances. Herein, a strategy for the synthesis of polysubstituted pyrrolizidine-3-ones by catalytic reductive domino-type recyclization of properly functionalized isoxazoline N-oxides was developed. The process is diastereoselective, and one diastereomer (out of four possible ones) is predominant in many of the studied cases. Using the developed method, modifications of potent GSK's PDE4 inhibitor and MSD's potent hNK1 antagonist were prepared.

Transition-Metal-Free, Atom- and Step-Economic Synthesis of Aminoketopyrrolizines from Benzylamine, Acylethynylpyrroles, and Acylacetylenes

A concise, atom-economic strategy for the synthesis of pyrrolizines with amino and keto substituents has been developed. It includes the following key steps: (i) the base-catalyzed (K₃PO₄/DMSO) addition of a benzylamine to 2-acylethynylpyrroles and (ii) noncatalyzed addition of enaminones obtained to the triple bond of acylacetylenes followed by intramolecular cyclization of the intermediate pentadiendiones thus formed to the target 1-(benzylamino)-2-acyl-3-methylenoacylpyrrolizines.