In connection with studies of the structure of carthamin derivatives, 2,5-bis(p-methoxycinnamoyl)-1,3,4,6,7,8- and 4,5-bis(p-methoxycinnamoyl)-1,2,3,6,7,8-hexamethoxyxanthene were synthesized. The comparison of these two hexamethoxyxanthenes with carthamin derivatives is described.
Model compounds of the precursor of carthamin 3, 4, and 5 were prepared. And in analogy with the precursor of carthamin (PRE) 1, they were converted into carthamin-type compounds 13, 14, and 15, respectively, when sprayed with peroxidase-H2O2 solution. It was also found that these conversions proceeded quantitatively by treatment with phosphate buffer extract of a cultured safflower cell and this conversion reaction proceeded by oxidative decarboxylation.
(+)- and (−)-Model compounds of a carthamin were synthesized. The absolute configuration of carthamin was deduced to be S, S by means of CD spectroscopy and X-ray analysis.
Carthamin acetate, (3S,3′S)-1-[5-(p-acetoxycinnamoyl)-3-C-(β-D-2″,3″,4″,6″-tetra-O-acetylglucopyranosyl)-3,4-dihydroxy-2,6-diketo]cyclohex-4-enylidene-1′-[5′-(p-acetoxycinnamoyl)-3′-C-(β-D-2″′,3″′,4″′, 6″′-tetra-O-acetylglucopyranosyl)-2′,3′,4′-trihydroxy-6′-keto]cyclohexa-1′,4′-dienylmethane 7a and its (3R, 3′R)-epimer 7b were synthesized via the C-glycosylation of 2-acetyl-1,3,4,5-benzenetetrol using