Pseudolaudanine

Demethylation of racemic laudanosine with 48 % hydrobromic acid (30) or anhydrous aluminum chloride (82) splits all four methoxyl groups and furnishes laudanosoline, but two or three methoxyl groups may be preserved if other reagents and milder conditions are chosen. When heated with 35 % hydrochloric acid at 100° for twenty minutes, all four possible monophenolic isomers are formed and may be isolated from the reaction mixture by fractional extraction and crystallization (83). They are lau-danine (LII) (m.p. 166-167°), pseudolaudanine (LIII) (m.p. 120-121°), DL-codamine (XXII) (oily), and pseudocodamine (LIV) (m.p. 129-130°). A discussion of their structure may be found on pages 57-63. 

The base LIII was also found by Burger (83) in the mother liquors of laudanine obtained by partial demethylation of DL-laudanosine (29). Vice versa, pseudolaudanine can be methylated to laudanosine (33, 42). 

The structure of pseudolaudanine was ascertained further by oxidation of its ethyl ether. Controlled oxidation yielded l-keto-2-methyl-6-ethoxy-... 

Racemic pseudolaudanine, C20H25NO3 (CXLIII Ri = H R2 = R3 = R4 = CH3) [mp 119°-120° methiodide, mp 211°-213°], has been prepared with improved yields by employing sodium borohydride in the reduction of the chloride CXLVI obtained by fusion of papaverine hydrochloride 123). 

---