Alain Bekaert

New total synthesis of bikaverin

On the basis of non-catalysed thermal condensation of a Mannich based with a phenol, followed by dehydration to an o.quinonic chromene further isomerized to a p.quinonic one, the synthesis of bikaverin 7 has been achieved via a six-step route involving selective dealkylation of bikaverin-dimethylether 6.

Crystal structure of 3-[(2,2-dimethylchroman-6-yl)carbonylamino]-7-hydroxy- 8-methyl-2-oxo-2H-chromen-4-yl toluene-4-sulfonate, C29H27NO8S

C29H27NO8S, monoclinic, P121/n1 (no. 14), a = 12.751(1) Å, b = 12.825(1) Å, c = 17.800(1) Å, 3 = 111.51(1)°, V = 2708.2 Å, Z = 4, Rgt(F) = 0.057, wRref(F) = 0.177, T = 293 K. Source of material A solution of para-toluenesulfonyl chloride (530mg, 2.78mmol, 1.1 eq.) in pyridine (5mL)was added slowly to an ice-cooled suspension of cyclonovobiocic acid (1.0 g, 2.53 mmol, 1 eq.) in dry pyridine (10mL).After stirring 24 h at room temperature, ethyl acetate (25 mL) was added, the organic layer washed with aqueous HCl 1 N (pH = 1-2), dried over Na2SO4 and concentrated under vacuum. Further purification by column chromatography on silica gel (cyclohexane/ EtOAc: 6/4) gave the title compound as a white solid (743mg, 1.35mmol, 53%, m.p. 163-165 °C). A slow evaporation of ethyl acetate solution leads to suitable translucent crystals for the crystallographic study. Experimental details The two H atoms participating in intermolecular hydrogen bonds (H1 and H15) were refined isotropically.