A novel pentacyclic pyridine dilactone. 7-methyl[1]benzopyrano[4,3-d][1]benzoxacino[4,3-b]pyridine-6,16-dione

When equimolar quantities of salicylaldehyde 2 and ethyl 3-amino-2-butenoate 3 or its constituents (ethyl 3-oxobutanoate and ammonia) were refluxed on a steam-bath for 6 hours with a trace of acetic acid, two products, a pentacyclic pyridine dilactone 4 and 3-acetyl coumarin 5 , resulted in 15% and 45% yields, respectively. The structure of 4 was elucidated as 7-methyl1]benzopyrano4,3-d]1]benzoxacino4,3-b]-pyridine-6,16-dione on the basis of its spectral data. The mechanism of its formation has been discussed. The reaction has been extended to three more substituted salicylaldehydes.