Structure of xanthalin

Conclusions

1. Xanthalin has been shown to have the structure of 2′, 2′-dimethyl-3′, 4′,-diangeloyloxy-3′, 4′-dihydropyrano-5′, 6′:6, 7-coumarin on the basis of the preparation of a number of derivatives and cleavage products.

2. The following products of the alkaline hydrolysis of xanthalin have been isolated and characterized for the first time: (±)-3′, 4′-dihydroxy-3′, 4′-dihydroxanthyletin (isokhellactone), C₁₄H₁₄O₅, with mp 213–215° C and (−)-trans-3′-hydroxy-4′-methoxy-3′, 4′-dihydroxanthyletin (isomethylkhellactone, C₁₅H₁₆O₅, with mp 136.5–138° C and [α] ²⁰_D −47.7 (ethanol).