Barry Sharpless, 11 and Curtis Adams11 Departments of Biochemistry and Microbiology, The University of Texas Health Science Center, San Antonio, Texas 78284, and Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Received July 18, 1986; Revised Manuscript Received December 10, 1986 abstract: The chemical synthesis of swainsonine [(15, 2/?, 8/?, 8a/?)-trihydroxyindolizidine] from trans-I, 4-dichloro-2-butene was previously described [Adams, C. E., Walker, FJ, & Sharpless, K. B.(1985) J. Org. Chem. 50, 420-424]. A modification of that synthesis provided two other isomers, referred to here as “Glc-swainsonine”[(15, 25, 8/?, 8a/?)-trihydroxyindolizidine] and“Ido-swainsonine"[(15, 25, 85, 8a/?)-trihydroxyindolizidine]. To determine whether these new compounds had biologicalactivity, they were compared to swainsonine as inhibitors of a number of commercially available glycosidases. While swainsonine is a potent inhibitor of jack bean-mannosidase but does not inhibit other glycosidases, its two isomers were inactive on-mannosidase but did inhibit other enzymes. Thus, Glc-swainsonine was an inhibitor of the fungal-glucosidase amyloglucosidase, and this inhibition was of a competitive nature (K¡= 5 X1ct5 M) with respect to the substrate p-nitrophenyl-D-glucopyranoside. This alkaloid also inhibited^-glucosidase, but much less effectively than-glucosidase. On the other hand, Ido-swainsonine was more effective toward^-glucosidase than toward-glucosidase, and this inhibition was also of a competitive nature. None of these inhibitors were effective against ß-mannosidase or a-or/3-galactosidase. Glc-swainsonine was also tested against the glycoprotein processing glycosidases. Surprisingly, in thisrespect, the alkaloid was like swainsonine in that it inhibited mannosidase II but had no effect or only slight effect on glucosidase I, glucosidase II, and mannosidase I. Glc-swainsonine also inhibited glycoproteinprocessing in cell culture. The oligosaccharide or oligosaccharides produced in the presence of Glc-swainsonine were hybrid types of structures similar to those seen in the presence of swainsonine and clearlydifferent from oligosaccharides induced by either castanospermine or deoxymannojirimycin. The inhibition of processing and of mannosidase II could not be due tothe presence of swainsonine in the Glc-swainsonine preparation, since this material did not inhibit jack bean-mannosidase, even at 10 pg/mL.

Swainsonine [(15, 2J?, 8J?, 8a/?)-trihydroxyindolizidine] is a plant alkaloid that was shown to be a potent inhibitor of lysosomal and other-mannosidases (Dorling et al., 1980; Kang & Elbein, 1983). This alkaloid was initially isolated from the wild, toxic Australian plant Swainsona canescens (Colgate et al., 1979) and more recently was found in locoweed (ie, Astragalus species) that grows in the southwestern areas of the US (Molyneux and James, 1982; Davis et al., 1984). It has also been found in the fungus Rhizoctonia leguminicola (Schneider et al., 1982). It is likely that the toxicosis that results from eating this plant is due to swainsonine (James & Hartley, 1977; Tulsiani & Touster, 1983b) as is the accu-mulation of high-mannose oligosaccharides in urine and other tissues (Abraham et al., 1983; Sadeh et al., 1983). Swain-sonine has also been found to be an inhibitor of glycoprotein processing (Elbein et al., 1981; Kang & Elbein, 1983b; Tulsiani