(1S)-(1.alpha.,4.alpha.,5.beta.,5a.beta.,6.beta.,8.beta.,9.beta.,9a.beta.)-Octahydro-5,8-dihydroxy-1,4-epoxy-6,9-methano-3-benzoxepin-7(2H)-one (a levoglucosenone derivative). The product of a 1,4-hydride shift