Chemoenzymatic synthesis of pyrrolo[2,1-b]quinazolinones:: Lipase-catalyzed resolution of vasicinone

A facile synthesis of bronchodilatory pyrrolo [2,1-b] quinazoline alkaloids by azidoreductive cyclization strategy employing TMSCl-NaI and bakers' yeast is described. Both the chemical and enzymatic methods are mild and take place at room temperature in good yields. Further, synthesis and resolution of vasicinone has been carried out by employing different lipases. It has been observed that lipase PS provides acetate of (S)-vasicinone in 98% ee.