Two alexines [3-hydroxymethyl-1,2,7-trihydroxypyrrolizidines] from Castanospermum australe

Chemoenzymatic Synthesis and Inhibitory Activities of Hyacinthacines A1 and A2 Stereoisomers

“…[5] These compounds differ in the C-7a configuration and this feature causes a differential activity against disaccharidase type a-glucosidases. [6] The compounds with the (S) configuration at C7a (alexine analogues) are scarce in nature, while a number with the (R) configuration have been reported. [4] Others, such as hyacinthacines A 1 and A 2 , have been recently isolated from the bulbs of Muscari armeniacum (Hyacinthaceae) and demonstrated to be good inhibitors against rat intestinal lactase, rat epididymis a-l-fucosidase, and amyloglucosidase from Arpergillus niger.…”

“…[13] The formation of four diastereoisomers of hyacinthacines A 1 and A 2 (Scheme 2, see experimental details in Supporting Information), namely (À)-hyacinthacine A 2 (6) [the enantiomer of (+)-hyacinthacine A 2 [19] ], 7-deoxy-2-epialexine (7) (the enantiomer of 3-epihyacinthacine A 2 [9] ), ent-7-deoxyalexine (8) (the enantioScheme 1. Retrosynthetic analysis for hyacinthacine stereoisomers.…”

Naturally Occurring Iminosugars and Related Alkaloids: Structure, Activity and Applications

“…When administered to various types of animal cells in culture, castanospermine prevented glycoprotein processing and therefore caused the production of N-linked glycoproteins having oligosaccharides mostly of the Glc 3 Man 9 GlcNAc 2 type [27][28][29]. C. australe coproduces a pyrrolizidine alkaloid, australine (12), which can be regarded as a ring-contracted form of castanospermine [30] but is a much weaker inhibitor of -glucosidases than castanospermine [31,32]. A highly hydroxylated pyrrolizidine alkaloid casuarine (13) and its 6-O--d-glucoside (14) have been isolated from the bark of Casuarina equisetifolia (Casuarinaceae) [33,34].…”

“…The known members of calystegines have been subdivided into three groups on the basis of the number of the hydroxyl groups present, namely calystegines A with three OH groups, B with four OH groups and C with five OH groups. Among calystegines, calystegines A 3 (28), B 1 (29), B 2 (30) and C 1 (31) …”

Naturally Occurring Pyrrolizidines: Inhibition of α-Glucosidase 1 and Anti-HIV Activity of One Stereoisomer

“…The latter two groups also have antiviral activity (Tyrns et al, 1990). Recently, the alexines have been purified from the complex mixture of plant alkaloids by solvent extraction and ion exchange chromatography (Choi et al, 1991;Nash et aI., 1992), and the inhibitory effects against cr and 13 glycosidase enzymes have been determined (Nash et al, 1990;Nash et al, 1992). In the present study, five of sixteen possible stereoisomers of alexine along with castanospermine and 6-epicastanospermine ( Fig.…”