New synthesis of (.+-.)-emetine from tetrahydroprotoberberine precursors via an .alpha.-diketone monothioketal intermediate

Conjugate Addition−Dipolar Cycloaddition Cascade for the Synthesis of Benzo[a]quinolizine and Indolo[a]quinolizine Scaffolds: Application to the Total Synthesis of (±)-Yohimbenone

“…Reoxidation of the resulting allylic alcohol mixture with manganese oxide provided enone 28 (Scheme ). The formation of intermediate 28 represents a formal synthesis of (±)-emetine ( 3 ) since 28 had been carried on to 3 by Takano and co-workers . Most importantly, the above cascade method represents a viable approach toward synthesizing compounds containing an isoquinoline substructure.…”

“…The resulting suspension was vigorously stirred for 72 h and then filtered through a Celite plug. The filtrate was concentrated under reduced pressure and purified using flash silica gel chromatography to give 0.07 g (75%) of the titled compound 28 as a yellow solid: mp 182−185 °C; IR (neat) 1667, 1513, 1464, 1369, 1249, and 1146 cm −1 ; 1 H NMR (C 6 D 6 , 600 MHz) δ 1.13−1.22 (m, 1H), 1.25−1.44 (m, 4H), 1.76 (t, 1H, J = 11.4 Hz), 1.96 (dt, 1H, J = 15.2 and 4.8 Hz), 2.23−2.35 (m, 4H), 2.44 (d, 1H, J = 16.2 Hz), 2.62 (d, 1H, J = 9.5 Hz), 2.63 (d, 1H, J = 11.4 Hz), 2.67−2.72 (m, 1H), 2.67−2.72 (m, 1H), 3.02−3.10 (m, 2H), 3.43 (s, 3H), 3.50 (s, 3H), 5.97 (s, 1H), 6.45 (s, 1H), and 6.56 (s, 1H); 13 C NMR (CDCl 3 , 150 MHz) δ 25.9, 29.1, 36.6, 40.3, 51.3, 55.8, 56.1, 61.9, 62.3, 108.0, 111.4, 125.4, 126.5, 128.7, 147.4, 147.7, 163.4, and 199.5.…”

An Update on Pharmacological Relevance and Chemical Synthesis of Natural Products and Derivatives with Anti SARS‐CoV‐2 Activity

“…Several efficient synthetic methodologies are available in the literature to synthesize emetine ( 66 ) [140–144] . Most of the synthetic procedures for the synthesis of 66 utilize homoveratrylamine [2‐(3,4‐dimethoxyphenyl)ethylamine] ( 67 ) as a starting material (Scheme 7).…”

“…Several efficient synthetic methodologies are available in the literature to synthesize emetine (66). [140][141][142][143][144] Most of the synthetic procedures for the synthesis of 66 utilize homoveratrylamine [2-(3,4-dimethoxyphenyl)ethylamine] (67) as a starting material (Scheme 7). [145] The reaction of homoveratrylamine ( 67 Finally, the pyridine ring of 73 was hydrogenated using H 2 /PtO to provide a racemic mixture of products (74), and from this racemic mixture, the desired emetine (66) can be isolated.…”

A conjugate addition-dipolar cycloaddition approach towards the synthesis of various alkaloids

“…50 However, a subsequent manganese oxidation of the crude reduction mixture cleanly converted the mixture to the known Takano enone 53, 51,52 thereby resulting in a formal synthesis of (±)-emetine. The related alkaloid (±)-yohimbenone was also synthesized using a similar approach.…”