New polyhydroxylated pyrrolizidine alkaloids from Muscari armeniacum:: structural determination and biological activity

Four new polyhydroxypyrrolizidines, hyacinthacines A(1), A(2), A(3) and B-3, have been isolated from the bulbs of Muscari armeniacum (Hyacinthaceae) in addition to the known hyacinthacine C-1, which was isolated from Hyacinthoides non-scripta (Hyacinthaceae). The structures of hyacinthacines A(1), A(2), A(3) and B-3 were identified on the basis of extensive NMR studies as (1S,2R,3R,7aR)-1,2-dihydroxy-3-hydroxymethylpyrrolizidine, (1R,2R,3R,7aR)-1,2-dihydroxy-3-hydroxymethylpyrrolizidine, (1R,2R,3R,5R,7aR)1,2-dihydroxy-3-hydroxymethyl-5-methylpyrrolizidine and (1S,2R,3R,5R,7R,7aR)-3-hydroxymethyl-5-methyl-1,2,7-trihydroxypyrrolizidine, respectively, or the corresponding enantiomers. The inhibitory activities of these new hyacinthacines against a variety of glycosidases are described. (C) 2000 Elsevier Science Ltd. All rights reserved.