CEBS-a method for the rapid assessment of gestation

A New Synthesis of Pongachalcone I, Glabrachromene, Mixtecacin, Candidin, Atalantoflavone Dimethylether, Racemoflavone Dimethylether, and Dihydropyranoaurones, and Their Analogues

“…The coupled doublets at 5.70 and 6.38 ppm (J= 10 Hz) in its *H-nmr spectrum are due to H-3 and H-4 of the pyran ring. Further, proton doublets at 7.73 and 8.00 ppm (J = 16 Hz) and the one-proton singlet at 13.60 ppm closely resembled those of chalcone la (19), in addition to the gem-dimethyl and aromatic protons, and were assigned to -, -ß, and 7-OH, respectively. These data indicate the structure 7-hydroxy-6-cinnamoyl-2,2-dimethylchromene for 4a.…”

“…A new and convenient synthesis of candidin [17a], atalantoflavone dimethylether [17b], racemoflavone dimethylether [17d], mixtecacin [20a], and their derivatives via the corresponding unknown dihydropyranoflavanones 13-15 has also been described.Pyranoflavonoids which possess interesting pharmacological properties (1-3) are known to occur mainly in the plant family Leguminosae. The naturally occurring flavonoids pongachalcone I, glabrachromene, candidin, and mixtecacin isolated from Pongamia glabra (4-6), Tephrosia candida (7), Tephrosia bracteolata (8), Tephrosiapraecans (9), and Tephrosia woodii (10) have a 2,2-dimethyl-2//-pyrano moiety as a part of their structure.Several methods have been developed (11)(12)(13)(14)(15)(16)(17) for synthesis of these flavonoids in the literature. However in these approaches the yields of the flavonoids were not appreciable.…”

“…Several methods have been developed (11)(12)(13)(14)(15)(16)(17) for synthesis of these flavonoids in the literature. However in these approaches the yields of the flavonoids were not appreciable.…”

“…Flavanones are isomeric with chalcones which are observed to by synthetic as well as biosynthetic precursors of the former group. Isomerization-cyclization of the chalcones 1 with acids forming dihydropyranoflavanones followed by dehydrogenation constitutes an important method among those hitherto known for the synthesis of pyranoflavones 16. Though dehydrogenation of dihydropyranoflavanone has proved useful for the synthesis of flavone, the overall yield of the flavone was poor; the reason being that the method (22) for deriving the precursor, viz., prenylated flavanone (from prenylbromide and corresponding flavanone), was not as productive and gave a mixture.…”

A Facile Synthesis of Isopongaflavone, Atalantoflavone Dimethylether, Racemoflavone Dimethyleter, and Methylenedioxy Isopongaflavone

“…Flavones possessing prenyl substituents and those with a 2,2-dimethylpyran ring system occur frequently (1,2). Since the naturally occurring pyranoflavanoids possess interesting pharmacological properties (3)(4)(5), several methods for their synthesis have been developed (6)(7)(8)(9)(10)(11)(12)(13)(14). There has been continued interest in our laboratory (15,16) in the synthesis of pyranoflavones from 0-hydroxyacetyl-2,2-dimethylchroman.…”