Beitrag zur Konstellation des Chelidonins und Erklärung einiger seiner Reaktionen

The Benzophenanthridine Alkaloids

“…IR: (CHC1,) 3210, 3206 (211) See also 21, 36, 104a, 163, 173, 296. 'H-NMR: 360 (CDCIj) (42) See also 36,173,189,227,287,296. 13C-NMR: 22.6 MHz (CDC1,) (296) MS: 353 (M+, 65), 352 (30), 336 (30), 335 (100) (287) CD: (EtOH)Aenm-1.63298, -0.79284 (0, + 1.72242 (i), +27.8,09, negative at shorter wavelengths; (EtOH-1%" HC1) -1.62298, -1.27287 (i), +0.89253, +2.62227 (i) Stylophorum (158,218,219,224,244) The following contain data for chelidonine with no stereochemical designation: [an: -138°(c=0.5,C,H,N) (211) See also 239. 255. Sources:…”

“…[a]22D: -100°±3°(c=0.50, CHC13)(239) [a]D: -112°±3°(c = 0.40, EtOH)(239) [a]D: -130°(c=0.5, C;H = N)(211) See also 104f.UV: (EtOH)239 (3.86), 288(3.91);Xmm 230(3.83), 257 (2.95) (1041, 278)See also 267.IR: (CHC13) 3344, 3288, 3285, 3200(211) See also 104f.…”

Total Syntheses of Chelidonine and Norchelidonine via an Enamide–Benzyne–[2 + 2] Cycloaddition Cascade

“…This tandem cascade possesses the unique feature of not only linking together the prevailing benzyne chemistry − with enamides that have become a highly versatile and accessible functional group − but also accentuating the less developed thermally driven [2 + 2] cycloaddition reaction manifold − while exploiting the powerful Oppolzer-type N- tethered IMDA strategy. − Accordingly, an application of this cascade in the synthesis of benzophenanthridine alkaloids [see 5 in the box] was pursued. In particular, we have been focusing on (+)-chelidonine 6 and (+)-norchelidonine 7 , which despite being known for well over a century, − remain an excellent proving ground for showcasing synthetic methods. , Our strategy would be based on the above cascade using benzyne precursor 9 and enamide 10 . We report here the total syntheses of (±)-chelidonine and (±)-norchelidonine.…”