No abstract

Halogeno-o-phenylenediamines and Derived Heterocycles.

No abstract

The structure of mycophenolic acid has been confirmed as (I) by infrared spectroscopy and by the synthesis of the degradation product, 6-carboxymethyl-6 : 7-dimethoxy-4-methylphthalide (X ; R = CH2*C02H) .FROM degradative studies by Raistrick and his co-workers 1-4 the structure of mycophenolic acid, a metabolic product of strains of Penicillium brevi-compactum, is almost certainly structure (I). Birkinshaw, Raistrick, and ROSS,, however, admitted slight doubts as to which of the two nuclear hydroxyl groups in normycophenolic acid (11) was methylated in mycophenolic acid and as to whether the potential hydroxymethyl group in the phthalide ring was ortho or meta to the nuclear methyl group. Though the fact that mycophenolic acid gipes a ferric chloride colour f suggests the hydroxy-phthalide system given in structure (I) , the phthalide carbonyl stretching frequency region of the infrared spectra shows maxima at 1742 (CHCl,), 1748 (CCl,), and 1751 cm.-l (dioxan) while the dimethoxycompound (111) shows maxima at 1763, 1776, and 1770 cm.-l in the same solvents, respectively, clearly indicating intramolecular hydrogen bonding as expected from structure (I). 7

After storage under ambient conditions zinc oxide, prepared by the combustion of metallic zinc, carries both carbonate and hydroxylic species. The former are removed by heating the oxide in oxygen and water vapour at 673 K. Subsequent coding to ambient temperatures in a moist oxygen atmosphere yields a surface carrying hydroxyls. The corresponding infra-red absorption spectrum exhibits four major absorption bands. Two narrow bands are present at 3670 and 3620 cm-' and two broad absorptions are centred about 3555 and 3440 cm-'. Outgassing the sample at 625 K removes the surface species corresponding to the 3555 cm-l band and reduces the concentration of that associated with the absorption at 3440 cm-l. The intensities of the 3670 and 3620 c m -l absorp-