複素環式化合物の合成研究(第181報) : 1-(α-Hydroxybenzyl)-2-methyl-1,2,3,4-tetrahydroisoquinoline誘導体のNMRスペクトルについて

抄録

Nuclear Magnetic Resonance spectrum of 5-hydroxy-1-(α-hydroxy-4-methoxybenzyl)-2-methyl-1, 2, 3, 4-tetrahydroisoquinoline (II) was measured and it was found that the methylproton of the methoxyl in 7-position and the ring proton at C-8 were shifted considerably to the higher magnetic field than their normal positions. Therefore, 1-(α-hydroxybenzyl)-2-methyl-1, 2, 3, 4-tetrahydroisoquinoline derivatives (III) to VII) were prepared by the oxidation of the corresponding 3, 4-dihydro-isoquinolines by alumina treatment followed by the reduction of its products with sodium borohydride. Examination of the NMR spectra of these compounds gave the same result as that of I. The reason for this shift was considered to be due to the fixation of the phenyl in the benzyl group at 1-position by the formation of an intramolecular hydrogen bonding between the lone-pair electrons of the tertiary nitrogen and the α-hydroxyl group, and the magnetic anisotropy of this fixation affects the methyl proton of the methoxyl group in the 7-position and the ring proton at 8-position. The formation of this intramolecular hydrogen bonding was proved by the dilution method in infrared spectrum.