Chapter 1 Erythrina and Related Alkaloids

Synthesis of the Tetracyclic Framework of the Erythrina Alkaloids Using a [4 + 2]-Cycloaddition/Rh(I)-Catalyzed Cascade of 2-Imidofurans

“…During the course of these studies, we encountered several novel rearrangement reactions. For example, when 13 was treated with polyphosphoric acid (PPA) in refluxing CH 2 Cl 2 , the rearranged benzo [4,5]azepino lactam 16 was isolated in 80% yield and its structure was unequivocally established by X-ray crystallography. This unusual reorganization can be rationalized by the pathway proposed in Scheme 4.…”

“…The solvent was removed under reduced pressure and the residue was purified by flash silica gel chromatography to give 0.04 g (87%) of 5-(tert-butyldimethylsilanyloxy) -1,4,5,6-tetrahydro-indol-2- 2.31 (ddd,J = 17.2,8.4 and 3.2 Hz),2.50 (dt,1H,J = 17.2 and 4.4 Hz),2.52 (ddd,1H,J = 16.0,10.2 and 2.0 Hz),2.87 (dd,1H,J = 16.0 and 4.4 Hz),4.03 (ddt,1H,J = 10.2,8.4 and 4.4 Hz),5.58 (ddt,1H,J = 4.4,3.2 and 2.0 Hz),5.78 (s,1H) and 8.61 (brs,1H); 13 C-NMR (CDCl 3 , 100 MHz) δ -4. 5,18.2,30.0,34.3,34.4,68.7,109.1,117.7,138.3,148.3 and 173.5;FAB HRMS Calcd for [(C 14 H 23 To a solution containing 0.06 g (0.24 mmol) of the above amide in 3 mL of DMF was added 0.02 g (0.54 mmol) of NaH (60%) at 0 °C. The mixture was stirred at 0 °C for 1.5 h, and then 0.22 g (0.9 mmol) of 4-(2-bromoethyl)-1,2-dimethoxybenzene was added.…”

“…5, 30.7, 36.7, 37.2, 39.1, 56.1, 56.6, 65.8, 72.0, 110.0, 112.7, 123.3, 127.2, 129.6, 147.0, 148.4, 161.5 6.28 (ddd, 1H, J = 9.6, 5.6, and 2.0 Hz), 6.69 (s, 1H), 6.81 (dd, 1H, J = 9.6 and 2.8 Hz) and 7.00 (s, 1H); 13 C-NMR (CDCl 3 , 100 MHz) δ 24. 5,27.1,34.9,37.0,55.8,55.9,64.6,108.5,112.0,118.7,123.9,126.2,128.5,136.1,146.8,148.1 and 158.0;HRMS Calcd. for [(C 18 H 19 .0, 37.3, 41.1, 55.9, 56.1, 65.9, 68.1, 107.8, 112.4, 121.3, 125.6, 126.5, 127.8, 133.5, 147.2, 148.7, 155.9, 159.9 and 170.6;HRMS Calcd.…”

Erythrina, a Potential Source of Chemicals from the Neotropics

“…Ghosal & coworkers mentioned that erysotrine is the most abundant alkaloid in bark of E. variegata var. orientalis but also has been identified the erysodine in a lesser amounts (Ghosal, et al, 1972), whereas Dyke & Quessy mentioned that only is found erysodine in the bark of the same species (Dyke & Quessy, 1981). In some species is frequent to find alkaloids to contain oxygenated functions in the C-8 and C-11 position of the erythrinane skeleton, still exist doubts respect if one species is synonym to other.…”

Caracterização dos alcaloides de Erythrina verna

“…Entre as técnicas analíticas para caracterização de alcaloides eritrínicos destaca-se o acoplamento da cromatografia em fase gasosa com a espectrometria de massas com ionização por elétrons, a qual oferece rápida análise dos extratos alcaloídicos e identificação baseada nos padrões de fragmentação de derivados eritrínicos (BOAR et al, 1970;MILLINGTON et al, 1974;DYKE;QUESSY, 1981). Tendo em vista a abundância dos dados de ionização por elétrons desses alcaloides na literatura, uma revisão publicada por AMER e colaboradores (1991) compilou dados de fragmentação com ionização por elétrons de mais de 90 derivados eritrínicos isolados de Erythrinae obtido através de síntese, além de informações espectrais de UV, IV e RMN, tornando-se uma referência de grande relevância para caracterização dessas moléculas.…”