Chemistry of naphthazarin derivatives. Transetherification selectivity of naphthazarin methoxy derivatives

Transetherification of naphthazarin methoxy derivatives in basic conditions occurs only with primary monohydric alcohols. 1,3-Butanediol due to the assistance of the hydroxy group at the C¹ atom gives rise to a mixture of transetherification products at the primary and secondary hydroxy groups in a ratio 3: 1. The reaction with methyl α-D-glucopyranoside affords predominantly methyl 6-O-(5,8-dihydroxy-1,4-dioxonaphthalen-2-yl)-α-D-glucopyranoside, previously unknown water-soluble naphthoquinone-carbohydrate conjugate.