Chapter 22, Problem 39P

Arbutin, a compound that can be isolated from the leaves of barberry, cranberry, and pear trees, has the molecular formula $C_{12}{H}_{16}{O}_7$. When arbutin is treated with aqueous acid or with a $\beta$ -glucosidase, the reaction produces D-glucose and a compound X with the molecular formula $C_6{H}_6{O}_2$. The ${}^{1}H$ NMR spectrum of compound X consists of two singlets, one at $\delta 6.8\left(4H\right)$ and one at $\delta 7.9\left(2H\right)$. Methylation of arbutin followed by acidic hydrolysis yields 2,3,4,6-tetra-O-methyl-D-glucose and a compound Y $\left(C_7{H}_8{O}_2\right)$. Compound Y is soluble in dilute aqueous NaOH but is insoluble in aqueous $NaHC{O}_3$. The ${}^{1}H$ NMR spectrum of Y shows a singlet at $\delta 3.9\left(3H\right)$, a singlet at $\delta 4.8\left(1H\right)$, and a multiplet (that resembles a singlet) at $\delta 6.8\left(4H\right)$. Treating compound Y with aqueous NaOH and ${\left(C{H}_3\right)}_{2}S{O}_4$ produces compound $Z\left(C_8{H}_{10}{O}_2\right)$. The ${}^{1}H$ NMR spectrum of Z consists of two singlets, one at $\delta 3.75\left(6H\right)$ and one at $\delta 6.8\left(4H\right)$. Propose structures for arbutin and for compounds X, Y, and Z.