Rauniticine-allo-oxindole B methanol monosolvate

Area of Science:

• Natural Product Chemistry
• Structural Chemistry
• Crystallography

Background:

• Uncaria longiflora is a plant species known for its potential medicinal properties.
• Oxindole alkaloids represent a class of natural products with diverse biological activities.
• Detailed structural elucidation of isolated compounds is crucial for understanding their properties and potential applications.

Purpose of the Study:

• To isolate and characterize a novel penta-cyclic oxindole alkaloid from Uncaria longiflora.
• To determine the three-dimensional structure of the isolated alkaloid using X-ray crystallography.
• To investigate the intermolecular interactions and crystal packing of the compound.

Main Methods:

• Isolation of the target compound from Uncaria longiflora.
• Single-crystal X-ray diffraction analysis to determine the molecular and crystal structure.
• Analysis of bond lengths, angles, and conformations of the rings within the molecule.
• Identification of hydrogen bonding networks and crystal packing motifs.

Main Results:

• The title compound, a penta-cyclic oxindole alkaloid (C(20)H(22)N(2)O(4)·CH(4)O), was successfully isolated and crystallized as a methanol solvate.
• X-ray crystallographic analysis revealed distinct conformations for the different rings: near-planar indole, envelope-shaped aliphatic ring, chair-shaped six-membered ring, and sofa-shaped oxygen-containing ring.
• A hydrogen bonding network involving the carboxylic acid group, methanol, and adjacent alkaloid molecules was identified, leading to the formation of chains and a layered structure.

Conclusions:

• The study provides the first detailed structural characterization of this specific penta-cyclic oxindole alkaloid.
• The observed crystal structure highlights specific conformational preferences and the significant role of hydrogen bonding in the self-assembly of the molecule.
• The findings contribute to the understanding of the structural diversity within oxindole alkaloids and their solid-state organization.