The effect of chelating substances on the orientation of hydroxymethyl groups in the reaction of phenol with formaldehyde is described.I t is found that when using hydroxides of the transition metals, Cu, Cr, Mn, Ni and Co, in aequous solution at p H = 4-5, hydroxymethylation occurs mainly at the ortho-position. Similar results were obtained with boric acid in benzene solution.Chelate formation in the transition state for ovtho-substitution is supposed to be the basic reason for the selective catalysis.
The coupling of L-histidine methyl ester and L-histidine-containing peptide esters to ferric protoporphyrin I X chloride is performed by the mixed carboxylic-carbonic acid anhydride method to give the disubstituted products in good yield : spectroscopic evidence indicates that the degree of interaction between the imidazole ligands and the iron atom depends upon the length of the peptide chain.
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