Synthesis of Licoisoflavone A and Related Compounds

Abstract

2′,4′,5,7-Tetrahydroxyisoflavone was partially benzoylated with benzoyl chloride to give 7-benzoyloxy-2′, 4′,5-trihydroxyisoflavone. The condensation of the 7-(benzoyloxy)isoflavone with 2-methyl-3-buten-2-ol, followed by the hydrolysis of the resultant 3′-(3-methyl-2-butenyl)isoflavone gave licoisoflavone A. Its 5′-(3-methyl-2-butenyl) isomer was also synthesized from 5-benzoyloxy-2′,4′,7-trihydroxyisoflavone in a similar manner.

Total Syntheses of Prenylated Isoflavones from Erythrina sacleuxii and Their Antibacterial Activity: 5-Deoxy-3′-prenylbiochanin A and Erysubin F

“…The conversion of chalcones into isoflavones requires not only an oxidation but also an aryl migration step after the cyclization, which is biosynthetically accomplished by the IFS enzymes. For chemical syntheses, Tl-(III)-acetate was demonstrated to induce oxidative aryl migrations of chalcones. , Although the method has been improved upon over the years, − the toxicity of the Tl-salts, which have to be used in excess, and occasionally poor selectivities remain serious drawbacks.…”

Phenolic compounds of the genera Glycyrrhiza L. and Meristotropis Fisch. et Mey. (review)

“…Also, convergent syntheses [145,146] and biosynthetic analysis of the results [6,7] in addition to modern physical chemical and instrumental methods [142 -144] should be used to determine the chemical structure of series of isolated licorice phenolic compounds.…”

Facile Total Syntheses of Two Novel 4-Alkenyloxy-2,6-dihydroxyacetophenones

“…The extract was washed with water, brine, and dried over anhydrous MgSO 4 , and evaporated under reduced pressure to give a solid residue that was puri®ed by ¯ash column chromatography on silica gel (petroleum ether±EtOAc, 10 :1) to aord 4 (2.96 g, 85%) as colorless needles, mp 94±96 8 8C (lit. 5 mp 96±98 8 8C). 2-Tolunesulfonyloxy-4,6-dibenzyloxyacetophenone (5).ÐA mixture of 4 (1.15 g, 3.3 mmol), TsCl (0.940 g, 5.0 mmol) and anhydrous K 2 CO 3 (4.45 g, 32 mmol) in dry acetone (100 mL) was re¯uxed under stirring for 6 h. After work-up, the residue was recrystallized from EtOAc±petroleum ether to give a colorless powder…”

“…5 mp 96±98 8 8C). 2-Tolunesulfonyloxy-4,6-dibenzyloxyacetophenone (5).ÐA mixture of 4 (1.15 g, 3.3 mmol), TsCl (0.940 g, 5.0 mmol) and anhydrous K 2 CO 3 (4.45 g, 32 mmol) in dry acetone (100 mL) was re¯uxed under stirring for 6 h. After work-up, the residue was recrystallized from EtOAc±petroleum ether to give a colorless powder…”