Stereoselective Synthesis of (3R)‐3,4‐Dihydro‐6,8‐dimethoxy‐3‐undecyl‐ 1H‐[2]benzopyran‐1‐one and Derivatives, Metabolites from Ononis natrix

Abstract

A short stereoselective synthesis of (3R) -3,4-dihydro-6,8-dimethoxy-3-undecyl-1H-[2]benzopyran-1-one and derivatives isolated from Ononis natrix has been described. Condensation of dodecanoyl chloride with 3,5-dimethoxyhomophthalic acid afforded 6,8-dimethoxy-3-undecylisocoumarin 3, which, on sequential saponification and esterification, yielded the keto ester 5. Enantioselective reduction of 5 with TarB-NO 2 /LiBH 4 directly furnished the title dihydroisocoumarin 1a in 80% ee (82% yield). Partial as well as complete demethylation of the latter provided the dihydroisocoumarins 1b and 1c, respectively. Diastereotopy of the CH 2 H-atoms on either side of the stereogenic center (C(3)) and the mass-fragmentation pattern of the dihydroisocoumarins have also been described. All of the compounds synthesized were examined in vitro for antifungal activity.

Dihydroisocoumarin from Xyris pterygoblephara active against dermatophyte fungi

“…Synthetic dihydroisocoumarins have been also described to be active against Trichophyton mentagrophytes (Saeed, 2003). Nevertheless, as far as we know this is the first report of a plant derived dihydroisocoumarin active against dermatophytic fungi.…”

Total synthesis of cytotoxic metabolite ( ± )-desmethyldiaportinol from Ampelomyces sp.

“…28, No. 3, 185-190, http://dx.doi.org/10.1080/14786419.2013 As a continuance of our focus on the synthesis and bioevaluation of this important class of secondary metabolites (Saeed 2003(Saeed , 2004(Saeed , 2013Saeed & Ehsan 2005;Saeed & Ashraf 2008;Saeed et al 2011), herein we report a simple and efficient total synthesis of the title compound as a racemic mixture. The synthesis not only confirms the structural assignment but also makes it accessible for comprehensive evaluation of its bioactivity.…”

An efficient total synthesis of ruprechstyril fromRuprechtia tangarana

“…We hereby report the conversion of 6,8-dimethoxy-3-pentylisocoumarin leading to initial formation of O-methylruprechstyril which could be regioselectively cleaved to ruprechstyril consequently avoiding the problem of the mixture formation. Thus, as a continuation of our interest towards synthesis of naturally occurring isocoumarins and their N, S analogues (Saeed, 2003), in this article, we wish to describe a short total synthesis of ruprechstyril.…”