Unequivocal NMR assignments: O -methoxymethyl esters derivatives of acid chromanones from Calophyllum brasiliense CAMB. (Guanandi) 

 - Natural Products Research, 22(10), 846-853, 2008 .
<br/><br/> Artículo 
<br/><br/> The present work describes the fractionation of the crude hexane extract (EBHEX) from Calophyllum brasiliense (Clusiaceae) stem bark. Derivatization of DCM2-9 fraction with diazomethane afforded the chromanones inophylloidic acid, isobrasiliensic acid, as well as, a mixture containing isobrasiliensic and brasiliensic acids, in the form of their more stable O-methoxy-methyl esters derivatives 1, 2, and 3, respectively. The isolation of 1 from C. brasiliense is described for the first time herein. The use of two-dimensional NMR methods ( 1 H-COSY, HMQC, and HMBC) allowed the precise determination of 13C and 1 H chemical shifts of compounds 1, 2, and 3. 
<br/><br/><label>Subjects--Topical Terms: </label><br/>CALOPHYLLUM BRASILIENSE<br/>ACID CHROMONONES<br/>UNEQUIVOCAL NMR ASSIGNMENTS