Conformation of xylocholine.

THE biological activity of quaternary aryloxyethylammonium salts is critically dependent on the nature and position of the substituents in the aromatic ring1–3. Thus choline phenyl ether bromide is a potent nicotine-like ganglion stimulant2,4, whereas its 2,6-dimethyl analogue (xylocholine) is devoid of ganglion stimulant activity5 but was the first compound to exhibit adrenergic neurone blocking activity6–9. Xylocholine also has muscarine-like properties6–9.