Other Phenolic Compounds Related to Mulberrofuran

In addition to mulberrofuran I (138) the reddish-violet powder on the surface of cultivated mulberry trees, gave five minor phenolic compounds, namely kuwanols A (139), B (140), mulberrofurans P (141), M (142), and Q (143). 

Kuwanol B (140) 118 a reddish-violet amorphous powder, [ah, + 103.5 , had molecular formula C34H26O8, and gave a hexamethyl ether (140a). Its acid solution of 140 had a red color which faded when neutralized. The UV spectrum of 140 had absorption maxima at 286 (12000), 310 (inflection, 13000), 326 (shoulder, 17000), and 336 nm (17000), which in acid solution showed bathochromic shifts as follows 286 (10000), 310 (inflection, 11000), 326 (14000), 336 (14000), 470 (shoulder, 2200), and 555 nm (4900). The same phenomenon was observed in the case of mulberrofuran I (138) 116). Formula 140 was proposed for the structure of kuwanol B, based on the spectral data. The C-NMR spectrum is listed in Table 5. It seems to be another derivative of a Diels-Alder type adduct such as kuwanon X (145) 114) and/or Y (144) 123), by the route already outlined in the case of mulberrofuran I (138) 116) (Fig. 35). 

Mulberrofuran P (141) 119), a blue amorphous powder, had molecular formula of C34H22O9, and gave a hexaacetate (141a). Its UV spectrum had absorption maxima at 210 (52000), 284 (15000), 315 (shoulder, 21000), 336 (34000), 351 (40000), and 370 nm (36000) it also showed a bathochromic shift in the presence of sodium methylate. Formula 141 was proposed for mulberrofuran P on the basis of spectral evidence. The C-NMR spectrum is listed in Table 5. The alkahne solution of 141 showed a blue color, while in a nitrogen atmosphere coloration did not occur. This coloration seems to be due to the formation of a K-complex between 141 and the quinoid substance (146) produced by autooxidation of 141. 

Mulberrofuran M (142) 120), an amorphous powder, [a]o -1-15°, had molecular formula C34H22O10, and gave a tetraacetate (142a). The UV spectrum had maxima at 208 (51000), 225 (inflection, 26000), 261 (20000), 299 (inflection, 18000), 323 (shoulder, 28000), 335 (34000) and 350 nm (shoulder, 28000), and was similar to those of other 4 -sub-stituted 6,3, 5 -trioxygenated 2-arylbenzofuran derivatives. The C-NMR spectrum of 142 is listed in Table 5. Hydrolysis of mulberrofuran M with 10% H2SO4 in methanol gave P-resorcylic acid methyl ester and a compound (142 ) were obtained. Considering the spectral data of 142,142 a, and 142, formula 142 was proposed for mulberrofuran M. 

Diels-Alder Type Adducts of Morns CeU Cultures 

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