Synthesis of Tenuilobine, a Bis-polyamine Alkaloid from Oncinotis tenuiloba, and Its Transamidation to Isotenuilobine

✍ Scribed by Martin K.-H. Doll; Armin Guggisberg; Manfred Hesse

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: German
• Weight: 464 KB
• Volume: 79
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19960790221

✦ Synopsis

From the leaves of Oncinotis tenuiloba STAPF, a novel polyamine alkaloid, tenuilobine (9). was isolated. This paper presents the synthesis of 9, as well as the base-catalyzed Zip reaction of 9, leading to the transamidation product isotenuilobine (10). The structure of 10 was further confirmed by 2D-NMR correlation spectroscopy. For analytical purposes, the his-polyamines 9 and 10 were converted into their pentaacetyl derivatives 12 and 11, respectively, which were readily separable by reverse-phase HPLC.

1. Introduction.

-Plants of the genus Oncinotis (Apocynaceae) are well-known for their content of polyamine alkaloids. Several different types of alkaloids have been isolated, ranging from simple monoacylated polyamines [I] to bi-or macrocyclic lactam alkaloids, all of them containing spermidine (1) as the basic component (Scheme I ) . However, tenuilobine (9) is the first spermine derivative which was isolated from Oncinotis species [2]. Moreover, since 9 contains not only spermine (3) but spermidine (1) as well, this compound can be classified as a bis-polyamine alkaloid, a hitherto unknown subdivision of naturally occurring polyamine derivatives. In general, neither from plants nor from animals [4], a substance was reported which contains two polyamine portions separated by an aliphatic moiety. The structure of tenuilobine (9) was elucidated by spectroscopic means and found to consist of hexadecanedioic acid being cross-linked with the secondary amino groups of spermidine (1) and spermine (3). To confirm these findings, we synthesized the alkaloid 9 as well as its unbranched isomer isotenuilobine (lo), which could not be detected in the plant extract. Scheme I a) H,N-(CH2)3-N-(CH2)4-NH, d ZHN-(CH,),-N-(CH,),-NHZ H 71 % H 1 2 H H