Chemical transformation of inocalophyllins, preparation of novel pyranocoumarines inocalocyclides

Lactonization of inocalophyllins A (5) and B (6) with toluenesulfonic acid has yielded four novel pyranocoumarins, designated inocalocyclides A-D (1-4). This reaction involved a rare elimination of an isoprene unit and an ene cyclization. (C) 2003 Elsevier Ltd. All rights reserved.