Chemistry of secologanin. Part 7: Chemical fragmentation of secologanin: biomimetic transition from the aliphatic into the aromatic skeleton

Privileged Biorenewable Secologanin-Based Diversity-Oriented Synthesis for Pseudo-Natural Alkaloids: Uncovering Novel Neuroprotective and Antimalarial Frameworks

Bioprivileged molecules hold great promise for supplementing petrochemicals in sustainable organic synthesis of a diverse bioactive products library. Secologanin, a biorenewable monoterpenoid glucoside with unique structural elements, is the key precursor for thousands of natural monoterpenoid alkaloids. Inspired by its inherent highly congested functional groups, a secologanin-based diversity-oriented synthesis (DOS) strategy for novel pseudo-natural alkaloids was developed. All the reactive units of secologanin were involved in these operation simplicity protocols under mild reaction conditions, including the one-step enantioselective transformation of exocyclic C8, C8/C11, and C8/C9/C10 as well as the chemoenzymatic manipulation of endocyclic C2/C6 via the attack by various nucleophiles. A combinatory scenario of the aforementioned reactions further provided diverse polycyclic products with multiple chiral centers. Preliminary activity screening of these newly constructed molecules led to the discovery of antimalarial and highly potent neuroprotective skeletons. The application of green biorenewable secologanin in diversity-oriented pseudo-natural monoterpenoid alkaloid synthesis might encourage the pursuit of valuable bioactive frameworks.

Absolute Configuration of Alkaloids from Uncaria longiflora through Experimental and Computational Approaches

The structure elucidation of three new alkaloids named isoformosaninol (1), formosaninol (2), and longiflorine (3), isolated from the leaves of Uncaria longiflora var. pteropoda (Miq.) Ridsdale, along with their biosynthetic pathways are discussed. Their absolute structures were determined through a combination of physical data interpretation and quantum chemical calculations using the time-dependent density functional theory (TDDFT) method.

Rigorous biogenetic network for a group of indole alkaloids derived from strictosidine

Strictosidine, the precursor of more than 2,500 indole alkaloids, was isolated from four species of three plant families. By searching the Dictionary of Natural Products on DVD it was found that about 150 indole alkaloids were obtained from the same species (coalkaloids), which is a direct proof of their common origin. On the base of their three-dimensional structure, taxonomic properties and standard reaction mechanisms an extended network was established which involved the four fundamental skeletons, the three types of carbon framework in the secologanin subunit and all major groups of indole alkaloids derived from secologanin and tryptamine (except a few minor groups, in which only less then 10 alkaloids were known). The system was extended to the heterodimer indole alkaloids and the quinoindole alkaloids as well.