Plantes de Nouvelle‐Calédonie. 94e Communication. Alcaloïdes monoterpéniques de Scaevola racemigera DÄNIKER

Abstract

Monoterpene Alkaloids of Scaevoiu racemigera DANIKERNine alkaloids have been isolated from the aerial parts of Scaevola racemigera. Two of them are the known compounds cantleyine (1) and tetrahydrocantleyine (2). The seven others are novel alkaloids, strychnovoline (3), 6-0-nicotinoylstrychnovoline (4), 6-0-nicotinoyltetrahydrocantleyine (S), 6-0-(5-vinylnicotinoyl)tetrahydrocantleyine (6), racemigerine (7), 6,7-epoxyracemigerine (8), and scaevoline (9). The structures of the new compounds have been elucidated by their spectral data and confirmed by chemical correlations. Moreover, the absolute configuration of 2, which had not been previously determined, has been elucidated.Le genre Scaevola L. (Goodeniactes) est constitut d'une centaine d'espices de plantes largement rtpandues dans les rtgions cijti6res des iles de 1'OcCan Indien et de l'Octan Pacifique [2]. I1 comporte, selon les auteurs, dix a douze esp6ces en Nouvelle-Caledonie [3-51 parmi lesquelles Scaevola racemigera DANKER [6] se distingue par son inflorescence en grappe spiciforme [4]. Des essais preliminaires rkalists par deux d'entre nous (J.P. et C.C.) ont montrk la presence d'alcaloides dans les parties aeriennes de cette espke. Compte tenu des donntes chimiques limittes disponibles sur la famille des GoodtniacCes et de l'absence de description d'alcaloides dans le genre Scaevola L., nous avons abordC l'ttude de Scaevola racemigera DANIKER. Ses parties aeriennes ont permis l'obtention de 0,25 YO d'alcaloides apr& extraction selon un protocole classique. Apr6s chromatographies successives sur colonnes de silice, neuf alcaloides ont ete isolCs. Leurs spectres UV les rattachent tous au groupe des alcaloides monoterpkniques.Deux de ces alcaloi'des ont Ct C identifies a des produits connus: cantleyine (1) [7-91 et tetrahydrocantleyine (2) [ 101. Cependant, la configuration absolue de la tttrahydrocantleyine n'avait pas Ct C anttrieurement determinte. Les sept autres alcaloi'des sont des produits nouveaux. I1 s'agit de la strychnovoline (3), de son ester nicotinique 4, des esters nicotinique et vinyl-Snicotinique de la tetrahydrocantleyine (5 et 6), de la racemigkrine ') 93e communication: [I].

Dehydration of Hydroxy-Hemiterpenoid Quinoline Alkaloids and Synthesis of Paraensidimerines

“…The structure of7 was deduced from its spectral data and confirmed by its alkaline hydrolysis to araliopsine [8] identical with an authentic sample (15). Dehydration of either 2 or 8 using toluene sulfonic acid or mesyl chloride (16) in alkaline solution afforded a complex mixture from which one major product was isolated. Its structure was established as the angular substituted furan 9 on the basis of its spec- tral data.…”

“…Formation of paraensidimerine D {13}, arising from a hetera Diels-Alder reaction, could be observed only when the reaction was carried out at 105°. Higher reaction temperatures (150 or 210°) led to the formation of classical Diels-Alder adducts, such as paraensidimerines A [14], C [15], and F [16]. In addition, isomeric dimers containing one 4-quinolone unit and one 2-quinolone unit were obtained when the reaction was performed at 150°.…”

Pyridine Monoterpene Alkaloid Formation from Iridoid Glycosides. A Novel PMTA Dimer from Geniposide

“…Repetition of the glucosidase/NH 4 OAc standard conditions on 7 , but at a tenfold diluted concentration of 7 , yielded a crude extract containing approximately 30−40% 16 , along with oligomers. Treatment of 7 aglycone under alternate PMTA formation conditions (eq 5) yielded racemigerine ( 17 ), a natural isolate from Scaevola racemigera …”

Phytochemical investigations of species of semi-arid Australian plants: A neglected area of research.

“…Amongst the secondary metabolites discovered in Scaevola spinescens, [17,18] the pyranocoumarins, iridoid glycosides, sesquiterpenoids and triterpenoids appear to exhibit a variety of biological activities that might be exploited in the development of medicinal agents. The occurrence of alkaloids within this family appears minimal with only limited investigations confirming their presence in non-Australian species [19,20] although these might be artefacts of extraction. Even less is known about alkaloid content in the Australian species, with a couple of Goodenia and Scaevola species showing their presence in field tests but nothing further is known.…”