Studies on the synthesis of safflomin-A, a yellow pigment in safflower petals: oxidation of 3-C-beta-d-glucopyranosyl-5-methylphloroacetophenone.
The direct C-glycosylation of methylphloroacetophenone 8 with d-glucose gave C-beta-d-glucopyranosylmethylphloroacetophenone (7) in 65% yield, which, on oxidation in the presence of small amount of pyridine under an oxygen atmosphere afforded the quinone 9, oxidized at the methylated position of the benzene ring as a pair of diastereomers in 27% yield. A detailed NMR analysis and a comparison of the UV-vis and CD spectra of their acetates indicated that the structure and stereochemistry of 9 was (1R,1'S,2R,3S,3aS,5R and 1R,1'S,2R,3S,3aS,5S)-7-acetyl-2-(1',2'-dihydroxyethyl)-5-methyl-3,5,6-trihydroxy-8-oxofuro[3,2-d]benzo[b]furan.
Sato
Shingo
S
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa-shi, Yamagata 992-8510, Japan. shingo-s@yz.yamagata-u.ac.jp
Nojiri
Toshikatsu
T
Onodera
Jun-ichi
J
D031187:Carthamus tinctorius / Q000737:chemistry*; D003373:Coumaric Acids / Q000138:chemical synthesis*; D035264:Flowers / Q000737:chemistry; D005960:Glucosides / Q000138:chemical synthesis* / Q000737:chemistry*; D010084:Oxidation-Reduction; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000737:chemistry; D010860:Pigments, Biological / Q000138:chemical synthesis*
C503192:3-C-glucopyranosyl-5-methylphloroacetophenone; D003373:Coumaric Acids; D005960:Glucosides; D010860:Pigments, Biological; C503191:safflomin A; D010696:Phloroglucinol