Secondary Metabolites Isolated from an Endophytic Phoma sp. – Absolute Configuration of Tetrahydropyrenophorol Using the Solid‐State TDDFT CD Methodology

Abstract

The known macrolide pyrenophorol (synonym helmidiol) (1), the new 2,3,10,11‐tetrahydropyrenophorol (3), and (4S,7R)‐4,7‐dihydroxyoctanoic acid (4), the monomeric acid of the sixteen‐membered cyclic diolide 1, were isolated from an endophytic Phoma sp. The relative configuration of tetrahydropyrenophorol (3) was confirmed by X‐ray single crystal analysis and its absolute configuration determined by the solid‐state TDDFT CD methodology. Compounds 1 and 4 show antifungal activity and the acid 4 is also an algicide. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Circular dichroism of diglycosyl dichalcogenides in solution and solid state

“…Since its absolute configuration is known, the main purpose here is to test our solid-state TDDFT CD approach [25][26][27][28] on a compound containing the diselenide moiety, to which applications of TDDFT calculations are scarce (TDDFT calculations on selenium-containing compounds: refs 37, 38).…”

An alternative stereoselective synthesis of (-)-1-tetrahydropyrenophorol

“…The alcohol (10) was then oxidized following treatment with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and [bis(acetoxy)iodo]benzene in aq. CH 2 Cl 2 , affording the corresponding carboxylic acid (11) in 75% yield, which, on desilylation with tetra-n-butylammonium fluoride (TBAF) in dry THF, gave the hydroxy-acid (2) [α] −68 (c 0.14, CHCl 3 )).…”

“…The residue was purified by column chromatography (60-120 Silica gel, 20% EtOAc in pet. ether) to furnish (10) 3435, 2958, 2855, 1727, 1614, 1520, 1369, 1299, 1174, 1012 (2). To a cooled (0 o C) solution of the octanoic acid (11) (1.1 g, 2.89 mmol) in dry THF (15 mL) under nitrogen atmosphere, TBAF (4.3 mL, 4.34 mmol) was added and stirred for 3 h. After completion of the reaction, the reaction mixture was diluted with water (5 mL) and extracted with ethyl acetate (2 × 50 mL).…”

“…In nature, macrodiolides are found as both homodimers [1][2][3][4] , consisting of two identical units and showing C 2 symmetry, and heterodimers 5 , consisting of two different units. Many of these macrodiolides (both homo and hetero) exhibit potent biological activities, such as antibacterial, antifungal, cytotoxic, and phytotoxic activity.…”

“…Its absolute configuration was determined by solid-state time-dependent density-functional theory (TDDFT) CD methodology. 2 Recently, a synthesis of (-)-1-tetrahydropyrenophorol was reported by Pratapareddy et al, 10 while Trost and Quintard 11 reported the total synthesis of (+)-tetrahydropyrenophorol. …”