No abstract

The absolute configuration of the spermine alkaloid 0-methylorantine (1) isolated from Chaenorhinum minus (L.) WILLK. ET LGE. and Ch. villosum (L.) WILLK. ET LGE. was determined. Besides the difference in the substitution at C (3 1) (OCH3 versus OH) the constitution of 1 and aphelandrine (2) [6] is the same. This was established by spectroscopic evidence, by isomerization reactions of 2, orantine (4) and their derivatives (Scheme 2), and by degradation reactions of 1 and 4, respectively. The methyl ether 1 of orantine (4), the latter prepared by base catalyzed isomerization from aphelandrine (2), is in all respects identical with the natural 0-methylorantine (1). Orantine (4) is identical (UV., CD., IH-NMR. and TLC. evidence) with ephedradine A, recently isolated by Hikino et al. [8], who determined the absolute configuration of ephedradine A by X-ray analysis. The absolute configuration of aphelandrine (2) was related to the one of 4 by chemical degradation. (-)-0-Methylorantin (1) wurde erstmals aus Chaenorhinum minus (L.) WILLK. ET LGE. und Ch. villosum (L.) WILLK. ET LGE. (Scrophulariaceae) isoliert [2] [3]. In beiden Pflanzen stellt diese Base das Hauptalkaloid dar. Hauptalkaloid anderer Chaenorhinum-Arten ist das Spermin-Alkaloid (+ )-Chaenorhin [2-41. Bei Untersuchungen der Gattung Aphelandra (Acanthaceae) wurde aus A. sinclairiana NEES als Nebenalkaloid ebenfalls (-)-0-Methylorantin (1) isoliert [S]. Hauptalkaloid aller uberprufter Aphelandra-Arten ist (+ )-Aphelandrin (2, Schema I)

The structure of the spermine alkaloid aphelandrine from Aphelandra sguarrosa NEES SummaryThe new spermine alkaloid aphelandrine (2) has been isolated from Aphelandra squarrosa NEES. By oxidation of 2 with KMn04 followed by methylation (CH2N2) 12 and 14 could be prepared (Scheme 2). Fusion of 2 with KOH yielded spermine (1) whereas hydrolysis of 2 in hot hydrochloric acid results in lacton 17, the structure of which could be elucidated by comparison with a synthetically prepared model compound (Scheme 3). The benzylic bonds N (lo), C (1 1) as well as 0 (16), C (17) of 2 could be cleaved by hydrogenolysis (compare 23 and 26; Scheme 4). The elucidation of the correct linkage of the spermine moiety with the aromatic dicarboxylic acid is based mainly on chemical and spectroscopic evidence of the tetrahydro derivative 26, the Hofmann-degradation products 28,30 and 31 (Scheme 6) as well as the ester 35, prepared by partial hydrolysis of 2 (Scheme 7).

The (2 Z, 4 E)-, (2 E , 4 Z)-and (2 E, 4 E)-isomers of 2,4-decadien-1-01 (5) have been obtained with high and predictable stereochemical homogeneity starting from both (2)-and (E)-1,4-decadiene. These hydrocarbons were hydroxylated in a reaction sequence consisting of metallation (by means of s-butyllithium or butyl-1ithiunVpotassium-t-butoxide, giving rise to organometallic intermediates of specific conformation), dimethoxyborylation and oxidation. The different decadienols as well as (2 E , 4 2)-2,4-undecadien-l-01 were converted into the isovalerates, the ester derived from (2 E , 4 Z)-2,4-decadien-l-ol being a natural flavor component.Allylmetall-Verbindungen treten in zwei bevorrech teten Konformationen auf, der ccendo,) -und der ttexo))-Form 1, die beide dank Koplanaritat grosstmoglichen Mesomenegewinn erzielen. Wahrend lithium-und magnesiumorganische Verbindungen vom Allyl-Typ in Sekundenschnelle das Torsionsgleichgewicht zwischen den ctendow-und ccexo>>-Formen einstellen, sind die entsprechenden Natrium-, Kalium-und Casium-Derivate bemerkenswert konformationsstabil. Ausgehend von (Z)-bzw. (E)-2-Alkenen lassen sie sich gezielt erzeugen. Wird die organometallische Zwischenstufe durch Einwirkung eines Elektrophils (El) hinreichend rasch in das Endprodukt 2 umgewandelt, so findet man die gleiche raumliche Anordnung der Substituenten an der Doppelbindung wieder, wie sie in der Alken-Vorstufe vorgegeben war. Wir sprechen dann von einer ccstereodefensivenw Reaktionsfolge.

A synthesis of 16,17-dihydrosecodin-17-ol and of secodine is described. Various indole derivatives were elaborated to a series of pyridinium salts, potential precursors for 1,2- and 1,6-dihydropyridine compounds exemplifying the proposed biointermediate 'dehydrosecodine.'