Calyciphyllines E and F, novel hepta- and pentacyclic alkaloids from Daphniphyllum calycinum

Total Synthesis of Four Classes of Daphniphyllum Alkaloids

The macrodaphniphyllamine-type, calyciphylline A-type, daphnilongeranin A-type, and daphnicyclidin D-type alkaloids are four structurally related classes of Daphniphyllum alkaloids. On the basis of a systematic analysis of the biogenetic network of these classes, we developed synthetic strategies centered on the C4-N and C1-C8 bonds of calyciphylline A, which took full advantage of the suitable substrates, reactions, and pathways that are altered from their counterparts in the postulated biogenetic network. Through this generalized biomimetic approach, we achieved the first synthesis of 14 Daphniphyllum alkaloids from the four subfamilies.

Structure revision and chemical synthesis of ligandrol's main bishydroxylated long-term metabolic marker

Although the main bishydroxylated long-term metabolite of the WADA-banned anabolic agent ligandrol (LGD-4033) is an important metabolic marker, it is not readily available in sufficient quantities to facilitate the development and validation of related analytical protocols or sensors. A chemically more robust structure was postulated as an alternative to the one previously established. The NMR spectra of the synthesized material and its LC-HRMS comparison with a relevant metabolic sample support the proposed structural revision.

Studies toward the Total Syntheses of Calyciphylline D-Type Daphniphyllum Alkaloids

An efficient construction of an aza-[5.7.6.5] tetracyclic core structure of calyciphylline D-type Daphniphyllum alkaloids has been achieved. The synthetic route features a diastereoselective cyclopropanation, efficient construction of the core bridged 8-aza-[3.2.1]octane skeleton through a [3 + 2] IMCC strategy, oxidative dearomatization of phenol, and gram-scale preparation in each step.

Calycindaphines A–J, Daphniphyllum alkaloids from the roots of Daphniphyllum calycinum

Ten new Daphniphyllum alkaloids, calycindaphines A–J (1–10), together with seventeen known alkaloids were isolated from the roots of Daphniphyllum calycinum. Their structures were established by extensive spectroscopic methods and compared with data from literature. Compound 1 is a novel alkaloid with a new rearrangement C₂₂ skeleton with the 5/8/7/5/5 ring system. Compound 2 represents the second example of calyciphylline G-type alkaloids. Compound 10 is the first example of secodaphniphylline-type alkaloid absent of the oxygen-bridge between C-25/C-29. The possible biogenetic pathways of 1 and 2 were also proposed. All the isolated compounds were evaluated for their bioactivities in three cell models. Compounds 22, 23, and 26 showed significant NF-κB transcriptional inhibitory activity at a concentration of 50 μM. Compounds 16 and 18 exhibited significant TGF-β inhibitory activity in HepG2 cells. Compounds 24 and 26 induced autophagic puncta and mediated the autophagic marker LC3-II conversion in HEK293 cells.

Ten new Daphniphyllum alkaloids, calycindaphines A–J (1–10), were isolated from Daphniphyllum calycinum. Compound 1 possesses a unique C₂₂ skeleton with the 5/8/7/5/5 ring system and might be a key intermediate for daphhimalenine A formation.

The chemistry of Daphniphyllum alkaloids

The triterpenoids Daphniphyllum alkaloids share the unique fused hexacyclic ring framework are isolated from the genus Daphniphyllum. These natural products possess comprehensive biological activities and exhibit excellent potential medicinal appliment. This review covers the reported isolation studies and biological activities of Daphniphyllum alkaloids spanning the period from 1966 to the beginning of 2020, In the meantime, the total synthesis of Daphniphyllum alkaloids will be emphatically summarized for supplement over this review series.

Direct Synthesis of Polycyclic Tropinones by a Condensation-[4+3]-Cycloaddition Cascade Reaction

A concise method of constructing polycyclic tropinone frameworks was developed. The single-step synthesis of polycyclic tropinone consists of an intramolecular [4+3] cycloaddition reaction of N-nosyl-pyrrole with oxyallyl cation that was generated in situ by an intermolecular condensation reaction of the nucleophilic functional groups on a tethered pyrrole with the aldehyde of 2-(silyloxy)-acrolein. This cascade reaction afforded various polycyclic tropinones including tri-, tetra-, and pentacyclic systems in high yields as single diastereomers.

Carbamoyl radical-mediated synthesis and semipinacol rearrangement of β-lactam diols

In an approach to the biologically important 6-azabicyclo[3.2.1]octane ring system, the scope of the tandem 4-exo-trig carbamoyl radical cyclization-dithiocarbamate group transfer reaction to ring-fused β-lactams is evaluated. β-Lactams fused to five-, six-, and seven-membered rings are prepared in good to excellent yield, and with moderate to complete control at the newly formed dithiocarbamate stereocentre. No cyclization is observed with an additional methyl substituent on the terminus of the double bond. Elimination of the dithiocarbamate group gives α,β- or β,γ-unsaturated lactams depending on both the methodology employed (base-mediated or thermal) and the nature of the carbocycle fused to the β-lactam. Fused β-lactam diols, obtained from catalytic OsO4-mediated dihydroxylation of α,β-unsaturated β-lactams, undergo semipinacol rearrangement via the corresponding cyclic sulfite or phosphorane to give keto-bridged bicyclic amides by exclusive N-acyl group migration. A monocyclic β-lactam diol undergoes Appel reaction at a primary alcohol in preference to semipinacol rearrangement. Preliminary investigations into the chemo- and stereoselective manipulation of the two carbonyl groups present in a representative 7,8-dioxo-6-azabicyclo[3.2.1]octane rearrangement product are also reported.

Calyciphyllines N-P, alkaloids from Daphniphyllum calycinum

Three new Daphniphyllum alkaloids, calyciphyllines N-P (1-3), were isolated from the leaves and stems of Daphniphyllum calycinum. The structures and relative stereochemistry of 1-3 were elucidated on the basis of spectroscopic data.

Alkaloids from the twigs of Daphniphyllum calycinum

Twelve new alkaloids, caldaphnidines G-R (1-12), along with 24 known ones, were isolated from the twigs of Daphniphyllum calycinum. Their structures were elucidated by spectroscopic methods, especially two-dimensional NMR techniques.

A Novel Alkaloid from the Seeds of Daphniphyllum calycinum

One novel alkaloid, named as caldaphnidine G (1), and two known alkaloid calycicine A (2), daphnezomine L (3) were isolated from the seeds of Daphniphyllum calycinum. The structure of 1 was established by spectral methods, especially 2D NMR techniques.