DL-Laudanosine

Solid

1-[(3,4-dimethoxyphenyl)methyl]-6,7-dimethoxy-2-methyl-3,4-dihydro-1H-isoquinoline is a member of isoquinolines.

This opium alkaloid occurs in the liquor following precipitation of Thebaine (q.v.) and is purified by extraction with small quantities of Et20, followed by precipitation with potassium iodide. The base crystallizes from hot C6H6 in small, colourless needles and has [α]15D+ 103.23° (EtOH). It is freely soluble in CHCI3, EtOH, Et20 or hot C6H6 but insoluble in H20 or alkalies. No colour is produced with FeCl 3 but with Fe203 and H2S04, a brown colour is formed, changing to green when warmed to ISOoC. With concentrated H2S04 alone, the alkaloid gives a rose-red colour, changing to deep violet at ISO°C. The solution of the alkaloid in EtOH is alkaline to litmus and both it, and its salts, are bitter to the taste. The crystalline methiodide has m.p. 218-221°C; [α]D+ 120°. The oxidation products with Mn02 and H2S04 are veratraldehyde, 2:3:6:7- tetramethoxy-9: I O-dihydroanthracene and laudaline (4: S-dimethoxy-2: - methylaminoethylbenzaldehyde, m.p. 123-4°C. On exhaustive methylation it yields trimethylamine and laudanosene (tetramethoxy-o-vinylstilbene). Laudanosine is one of the most convulsant of the opium alkaloids but possesses only a slight analgesic action.

light yellow fine crystalline powder

Crystallise these from EtOH. The (±)-picrate crystallises from EtOH with m 177-178o. The (-)-isomer has m 83-85o and

DL-Laudanosine is an intermediate in synthesizing (S)-Laudanosine (L178525), a metabolite of the neuromuscular-blocking drugs Atracurium (A794500) and Cisatracurium (C496700) with potentially toxic systemic effects. It crosses the blood-brain barrier and may cause excitement and seizure activity.