The Calyxolanes:  New 1,3-Diphenylbutanoid Metabolites Isolated from the Caribbean Marine Sponge Calyx podatypa

Abstract

Calyxolanes A (1) and B (2) are rare 1,3-diphenylbutanoid compounds isolated from the marine sponge Calyx podatypa collected in Puerto Rico. Their structures, including relative stereochemistry, have been determined by spectroscopic methods. The unique 2,4-diphenyloxolane function in 1 and 2 was established by 2D 1H-1H and 1H-13C NMR correlation experiments and confirmed by mass spectral analysis. A suggestion is made as to their biogenetic origin.

Asymmetric Hydrogenation of Furans and Benzofurans with Iridium–Pyridine–Phosphinite Catalysts

“…Typical examples of natural tetrahydrofuran derivatives are marmelo oxide A and its diastereomer marmelo oxide B,2 or the diastereomeric calyxolanes A and B, isolated from the marine sponge Calyx podatypa (Figure 1). 3 Biologically active dihydrobenzofuran‐derived natural products include conocarpan,4 corsifuran A,5 and thespesone ( 1 ), isolated in 1983 from the heartwood of the tree Thespesia populnea 6. Recently, a first total synthesis of 1 and its non‐natural enantiomer was reported, along with its cytotoxic activity against a small panel of human cancer cell lines.…”

Intermolecular Electrophilic Addition of Epoxides to Alkenes: [3+2] Cycloadditions Catalyzed by Lewis Acids

“…2‐methylstyrene) are tolerated and provide a small increase in diastereoselecivity (3.2:1 dr for example 7h ). To demonstrate the potential utility of this method in synthesis, cycloaddition between styrene and styrene oxide provided a mixture of the diastereomeric natural products Calyxolanes A ( 7g , anti diastereomer) and B ( 7g , syn diastereomer) in a single step . As evidence of the mild reaction conditions, a ferrocene‐substituted alkene survived the reaction unscathed and provided the corresponding tetrahydrofuran 7e .…”

Iridium-catalyzed enantioselective allylation of silyl enol ethers derived from ketones and α,β-unsaturated ketones

“…5 Finally, in an effort to demonstrate the practicality and utility of this catalytic process, we examined the application to the total synthesis of marine natural products calyxolanes (Figure 1). 12 Calyxolane A and B are rare 1,3-diphenylbutanoid compounds isolated from the marine sponge Calyx podatypa collected in Puerto Rico by Rodriguez and co-workers in 1997. Due to the scanty samples of natural source, their bioactivities and absolute stereochemistry are still unknown.…”