Iminium salts from .alpha.-amino acid decarbonylation. Application to the synthesis of berbines

Total synthesis of (.+-.)-chelidonine

“…The column was eluted with CHCI3 (125 mL). The eluant was concentrated, hexane was added, and the solution was cooled in the freezer to obtain the product as a yellow, crystalline powder: 18.20 g (72%); mp 93-95 °C; IR (KBr) 2230,1699,1458,1430,1296,1262,1231,1208,1130,1040,1021 cm"1; NMR & 7.01 (s, 2 ), 6.19 (s, 2 ), 4.50 (q, 2 H, J = 7 Hz), 4.07 (s, 2 ), 1.39 (t, 3 H); mass spectrum, m/e (relative intensity) 233 (57), 205 (46), 204 (26), 188 (75), 187 (100), 177 (21), 174 (19), 160 (19), 159 (50), 149 (19), 102 (20), 77 (26), 76 (26), 75 (27), 63 (19), 51 (27), 50 (20).…”

“…A second route to the benzyl chloride 7 was based on the recently reported conversion of [(3,4-dimethoxyphenyl)methyl]dimethylamine ( 16) to ethyl 6-(chloromethyl)-2,3-dimethoxybenzoate (17). 19 Since large quantities of the Schiff base 8 were already on hand for later use in the synthesis (Scheme II), the required compound 10 was prepared from 8 by reduction and methylation. Metalation of the amine 10 with n-BuLi followed by addition of excess ethyl chloroformate to the ortholithiated intermediate did afford the desired benzyl chloride 7.…”

Use of chloroalkenylamines for the synthesis of 1-azabicyclo[3.3.0]octane and 1-azabicyclo[4.3.0]nonane derivatives

“…The first of these, (6), is disfavoured and we have found none that is successful. The third, (8), and fourth, (9), are favoured and we have indeed found that some, though not all, are Cl 5endoondot r i g 5 ondo -0 x 0t r i g ( 6 ) ( 7 ) 5 -0 x 0 -ondot r i g ( 8 ) Cl 5 -8x0 -0 x 0 -trig ( 9 ) productive. The second type, (7), is a borderline case (models), but we had no success in the several examples tried.…”

Die Synthese des Octacidomycins

“…Zur selektiven Erzeugung des 7-Anions entfielen allerdings Basen wie Natrium oder Natriumethanolat in Xylol oder siedendem Benzol ","). Eher geeignet erschien Natriumhydrid in DMF 13), das jedoch keine Umsetzung ergab. Auch nach Einsatz von LDA bei -78°C versagte die Alkylierung zunachst, sogar bei + 20°C.…”