Furochromone khellin

A plausible pathway is that the aromatisation of the cyclohexadienone 92 by a proton shift is accelerated in the presence of Ac20 under formation of acetate 93. The simultaneously generated acetic acid then cleaves the acetate to form the free phenol 94 (Scheme 44). This effect was observed for the first time during studies towards the total synthesis of the lipid-alternating and anti-atherosclerotic furochromone khellin 99 [64].The furanyl carbene chromium complex 96 was supposed to react with alkoxyalkyne 95 in a benzannulation reaction to give the densely substituted benzofuran derivative 97 (Scheme 45). Upon warming the reaction mixture in tetrahydrofuran to 65 °C the reaction was completed in 4 h, but only a dimerisation product could be isolated. This... 

Initial observations on khellin (32), a furochromone-type compound from Ammi visnaga L., showed a mast-cell stabilizing effect. This led to the synthesis of many derivatives of this lead for the potential treatment of allergy and asthma, most notably the approved preventive antiasthma drug, cromolyn sodium (33). The precise molecular mechanism of this class of drugs is not yet clearly imderstood. ... 

Furochromones are group of coumarins, derived from y- benzopyrone. They are related to furanocoumarins and are present in plants of family Apiaeeae and Rutaceae. Ammi visnaga is a potential souree of furoehromones like khellin and visnagin. Khellin was onee used as coronary vasodilator drug. 

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