Synthesis and Extraction of Pentalongin, A Naphthoquinoid From Mitracarpus Scaber

MS/MS-Guided Isolation of Clarinoside, a New Anti-Inflammatory Pentalogin Derivative

“…It is well known to contain phenols [5], flavonoid glycosides [5], furanocoumarines [5], terpenes [6], alkaloids [7] and pentalongin derivatives [8,9]. Herein, we report the identification of clarinoside (1), a new pentalongin derivative exhibiting the rare quinovose moiety along with the known harounoside (2).…”

A Survey of Synthetic Routes towards the Pyranonaphthoquinone Antibiotic Pentalongin and Syntheses of the Corresponding Nitrogen Derivatives

“…39 Although the last step is the same, these authors performed the Lemieux-Johnson oxidation on the quinone 67, a lower-yielding reaction (Scheme 11).…”

“…In the course of our research, an alternative pathway, also built up around a Lemieux-Johnson oxidation, was published. 39 Although the last step is the same, these authors performed the Lemieux-Johnson oxidation on the quinone 67, a lower-yielding reaction (Scheme 11).…”

Synthesis of Pyranonaphthoquinone Antibiotics Involving the Phthalide Annulation Strategy

“…In the past years, our department has managed to synthesise a particular group of pyranonaphthoquinones such as pentalongin (1), 8,9 dehydroherbarin (2) 10 1,3-disubstituted-3,4-dehydropyranonaphthoquinones 3 11 tetracyclic pentalongin derivatives 4 12 and harounoside (5, Figure 1). 13 The naphtho [2,3-c]pyran skeleton was constructed before by ring closure of 2-allyl-3-hydroxymethyl-1,4dimethoxynaphthalenes 10 and 2-allyl-3-hydroxymethyl-1,4-naphthoquinones, 14 by intramolecular base-catalysed condensation of 3-bromomethyl-1,4-dimethoxy-2-naphthaleneacetic acid, 15 by palladium-catalysed intramolecular cyclisation of 2-bromo-3-aryloxymethyl-1,4-naphthoquinone, 12 by ring-closing metathesis of a vinyl ether, 9 by using chloromethylation of substituted-2-naphthylacetic acid 16 and by reaction of 2-(1-hydroxyalkyl)-l,4-naphthoquinones with enamines or imines. 17 In this report, a novel efficient route towards pentalongin is described, utilising a phthalide annulation strategy, which allows the synthesis of novel pyranonaphthoquinone derivatives which are not accessible by other routes.…”