Beiträge zur Kenntnis des Phlorrhizins und des Quercitrins

Flavonoids From the Leaves of Kalmia latifolia

“…For details, see the Experimental section. bTlc Rf values with Solvent System A. also at 165° ( 9). Our material, obtained after several days treatment with acetic anhydride in pyridine at room temperature, melted at 169°and exhibited an -nmr spectrum not in accord with a tetraacetate structure.…”

“…First, the 4'-glucoside is known ( 16) and has mp 69-70°( hydrated) and 110°( anhydrous). Second, methylation of glucoside 14 followed by hydrolysis afforded in good yield 2',4,4l-trimethylphoretin (19), identical with the trimethyl ether prepared from phloridzin (1) in the same manner.…”

“…Since the melting point was significantly higher (by 94°) than our triacetate, the original structure proposed appeared in doubt, although the existence of polymorphs was a possibility. Repeating the hydrolysis as stated (14) gave a crystalline product, mp 195.5-7.0°in reported yield, but the spectral data were inconsistent with a triacetate. The -nmr spectrum contained a single three-proton singlet for an acetate at 2.23 ppm.…”

“…The Cand C-ß carbons were located in this matter and provide support for the enol acetate structure 6. It is clear that the phloretin acetate of the literature (9) with reported mp 165°must be formulated as the pentaacetate 6.…”

“…Treatment of the monoacetate 8 with diazomethane produced 4-acetyl-2',4'dimethvlphloretin (9), whose structure was determined from spectral data. The phenolic group at 13.99 ppm in the -nmr spectrum requires an intramolecular hydrogen-bonded location, and the two very intense peaks in the mass spectrum at m/e 181 and 154 for fragments 10 and 11, respectively, place the methyl ethers in the phloroglucinol ring.…”