Absolute Stereochemistry of Citrinadins A and B from Marine-Derived Fungus

Abstract

[Structure: see text]. Citrinadin A (2) is a pentacyclic indolinone alkaloid isolated from the cultured broth of a fungus, Penicillium citrinum, which was separated from a marine red alga. The absolute stereochemistry of the pentacyclic core in 2 and its new congener, citrinadin B (1), was elucidated by analysis of the ROESY spectrum for the chlorohydrin derivative (3) of 1 as well as comparison of the electronic circular dichroism (ECD) spectra for 1 and 2 with those of known spirooxiindole alkaloids. On the other hand, the absolute configuration at C-21 bearing an epoxide ring was assigned as S by comparison of the vibrational circular dichroism (VCD) spectra of 1 with those of model compounds 2S- and 2R-2,3-epoxy-3,3-dimethyl-1-phenylpropan-1-one (4a and 4b, respectively).

Molecular diversity of spirooxindoles. Synthesis and biological activity

“…There have been described interesting examples of the intramolecular Friedel-Crafts reaction for the synthesis of diversely functionalized spirooxindoles [195,196]. In the latter case, compounds 347 can be derived from readily accessible α-keto-N -arylacetamides 346 bearing alkyl side chain residues in the presence of trifluoroacetic acid (TFA) at room temperature or at 45 • C. This method could be applied for the synthesis of spirooxindoles fused with cyclopentyl-, cyclohexyl and cycloheptyl rings (Scheme 100).…”

Structural determination of molecular stereochemistry using VCD spectroscopy and a conformational code: Absolute configuration and solution conformation of a chiral liquid pesticide, (R)‐(+)‐malathion

“…For flexible large molecules, such as natural products, the absolute configurations have been often determined by the model fragments of the entire molecules. 25,26 Therefore, we have addressed the conformational search using DFT calculations for the fragments of entire molecules in combination with the conformational code.…”

Chrysogenamide A from an Endophytic Fungus Associated with Cistanche deserticola and Its Neuroprotective Effect on SH-SY5Y Cells

“…1 was a new member of this group of compounds, it possessed a skeleton expected to be an intermediate in the biosynthesis of the citrinadins A and B reported as a novel class of pentacyclic spiroindolinone alkaloids in 2005 [18]. From the structural point of view, it is important to point out that 1 is a unique structure with methylation at position C-17 and a 2-oxindole moiety possessing an isoprene unit at C-7.…”