Development of a Divergent Synthetic Route to the Erythrina Alkaloids: Asymmetric Syntheses of 8‐Oxo‐erythrinine, Crystamidine, 8‐Oxo‐erythraline, and Erythraline

Abstract

A general synthetic methodology toward the erythrina alkaloids has been developed. Inspired by a proposed biosynthetic mechanism, the medium-sized chiral biaryl lactam was asymmetrically transformed into the common core A-D rings by a stereospecific singlet oxygen oxidation of the phenol moiety, followed by a transannular aza-Michael reaction to the dienone functionality. The late-stage manipulation of the oxidation and oxygenation states of the functional groups on the peripheral moieties enabled the flexible syntheses of the erythrina alkaloids.

Gas‐phase dissociation study of erythrinian alkaloids by electrospray ionization mass spectrometry and computational methods

“…The bark of these species has also been employed to treat disorders of the nervous system such as insomnia, depression and epilepsy. [11,12] These applications agree with the biological action reported for isolated erythrinian alkaloids [2,3,5,9,10] and have led to the launch of several products into the pharmaceutical market. However, only a few studies about the absorption, distribution, metabolism and elimination (ADME) of these alkaloids have been published.…”

Bioassay‐guided isolation of potent aphicidal Erythrina alkaloids against Aphis gossypii from the seed of Erythrina crista‐galli L

“…2. In addition, biogenetic considerations on Erythrina alkaloids 20,32,33 and the identical chemical shift of C-3 with known compounds [34][35][36][37] suggested that 1 has an R configuration at C-3. The absolute configuration of C-10 was assigned as R from the Pest Manag Sci 2018; 74: 210-218 NOESY, which indicated that there was an interaction between H-10 and H-4 (Fig.…”

Synthetic Studies on Heteropolycyclic Natural Products: Development of Divergent Strategy

“…It was next envisioned to reduce the γ-lactam moiety without affecting the other functional groups in the molecule. Consequently, amathaspiramide D (45) was subjected to reduction with Schwartz's reagent (Cp 2 Zr(H) Cl); the secondary lactam was directly reduced to the cyclic imine [93][94][95] without affecting the C-6 tertiary amide or C-8 N-acyl hemiaminal, affording amathaspiramide E (46) in 67% yield (Chart 6). The imine moiety in 46 could be selectively reduced under reductive methylation conditions, which furnished amathaspiramide A (42) in 78% yield.…”