<unk>  is the<unk> trorotatory enantiomer of levomethorphan, which is the methyl ether of levorphanol, both opioid analgesics. It is named according to IUPAC rules as (+)-3-methoxy-17-methyl-9α,13α,14α-morphinan. As its pure form,<unk>  occurs as an odorless, opalescent white powder. It is freely soluble in chloroform and insoluble in water; the hydrobromide salt is water-soluble up to 1.5 g/100 mL at 25 °C.<unk>  is commonly available as the monohydrated hydrobromide salt, however some newer extended-release formulations contain<unk>  bound to an ion-exchange resin based on polystyrene sulfonic acid.<unk> 's specific rotation in water is +27.6° (20 °C, Sodium D-line). Synthesis Several routes exist for the synthesis of<unk> . Even though many of the syntheses have been known since the middle of the 20th century, researchers are still working today to further develop the synthesis of<unk>  and, for example, to make it more environmentally friendly. This includes the synthesis by means of ionic liquids. Racemate separation Since only one of the stereoisomers has the desired effect, the separation of a racemic mixture of hydroxy N- methyl morphinan using tartaric acid and subsequent methylation of the hydroxyl group is a suitable method. By using (D)-tartrate, the (+)-isomer remains as the product. Racemate separation for synthesis of<unk>  This synthetic pathway was patented by Roche in 1950. Traditional synthesis The traditional synthetic route uses Raney nickel and has been further improved over time, for example by the use of ibuprofen and ACl3. center Overall, it is a cost-effective method with moderate reaction conditions that is easy to handle and suitable for industrial production. Grewe's cyclization center Grewe's cyclization is easier to handle in terms of the chemicals used, produces higher yields and higher purity of the product. Improved Grewe's cyclization Formylation prior to cyclization avoids ether cleavage as a side reaction and yields higher than without N-substitution or N-methylation. In this example, the purification was done by formation of a brucine salt. center This process has also been patented by Roche.
Dextromethorphan
Nalorphine
Pethidine
Dextrorphan
Aceclidine
Betamethadol
Fentanyl
Procaine