Asymmetric synthesis of 5,7-O-dimethyleucomols via enantioselective oxidation of enol phosphates

The asymmetric synthesis of some derivatives of the homoisoflavone class, (S)-(−)- and (R)-(+)-5,7-O-dimethyleucomols, and (−)-homoisoflavone epoxide, based on the asymmetric oxidation of the corresponding enol phosphates, is described. The influence of electronic and steric effects of the enol phosphate substituents on the facial stereoselectivity of oxidation was observed.

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(3R)-3-Hydroxy-5,7-dimethoxy-3-(4-methoxy-benzyl)-chroman-4-oneC19H20O6ee >99% (HPLC)[α]D20 = +70 (c 0.2, CHCl3)Source of chirality: asymmetric synthesis with DHQD/PHALAbsolute configuration: (R)

7a-(4-Methoxybenzyl)-4,6-dimethoxy-1aH-oxireno[2,3-b]chromen-7(7aH)-oneC19H18O6ee = 83% (HPLC)[α]D20 = −17 (c 0.2, CHCl3)Source of chirality: asymmetric synthesis with a chiral dioxirane