(2S,3′S,3a'R,5′R,7a'R)-5′-[(E)-5-(Furan-3-yl)-2-methylpent-1-en-1-yl]-3-hydroxy-3′,4,7′-trimethyl-1′,2′,3′,3a',5′,7a'-hexahydro-5H-spiro[furan-2,4′-inden]-5-one

Abstract

The title compound, ircinianin, C25H32O4, belongs to the sesterterpene tetronic acid compound family and was isolated from the marine sponge Ircinia wistarii. These chemical scaffolds are pharmacologically relevant, since they represent a new class of glycine receptor modulators. The furan ring makes a dihedral angle of 35.14 (12)° to the 4-hydroxy-3-methylfuran-2(5H)-one ring. The crystal packing is characterized by intermolecular O—H...O hydrogen bonds, which generate [010] chains.

Discovery of Ircinianin Lactones B and C—Two New Cyclic Sesterterpenes from the Marine Sponge Ircinia wistarii

“…Existing RP-LC fractions from a former study [ 26 ] were chromatographed repeatedly over RP-HPLC to yield pure compounds 3 – 8 , respectively. The known compounds were readily identified via HR-MS and MS n spectroscopic measurements or by comparing their NMR data with those reported in the literature (see Supporting Information ) [ 30 ].…”

“…Eleven fractions were gained. For the detailed extraction and fractionation protocol, see Majer et al [ 26 ]. Based on the analysis by HPLC-DAD and LC-MS the 50%, 70% and 90%-MeOH fraction were identified as containing ircinianin-like sesterterpenoids.…”

“…In the 1990’s, the structure was confirmed by total synthesis and the full stereostructure was assigned [ 25 ]. In 2020, natural-derived ircinianin ( 1 ) was effectively crystalized to enable confirmation of the absolute structure [ 26 ].…”

“…The current study describes the work-up of these fractions, which led to the isolation and structural elucidation of two new ircinianin lactones ( 7 and 8 ), along with a suite of ircinianins previously reported that include oxo-ircinianin ( 3 ), ircinianin lactam A ( 4 ), oxoircinianin lactam A ( 5 ) and ircinianin lactone A ( 6 ). Since from our first study [ 26 ], high amounts of crystalline ircinianin ( 1 ) were still available, an in-depth screen for biological activity was conducted in parallel, which led to the discovery of a moderate antiprotozoal activity for 1 .…”

“…During our early work to isolate and determine a refinded X-ray structure of ircinianin ( 1 ) from the exisiting Ircinia wistarii sample [ 26 ], it became apparent that several ircinianin derivatives were present in adjacent fractions. The current study describes the work-up of these fractions, which led to the isolation and structural elucidation of two new ircinianin lactones ( 7 and 8 ), along with a suite of ircinianins previously reported that include oxo-ircinianin ( 3 ), ircinianin lactam A ( 4 ), oxoircinianin lactam A ( 5 ) and ircinianin lactone A ( 6 ).…”