Synthesis of 1-homoaustraline

Synthesis of iminosugars via 1,3-dipolar cycloaddition reactions of nitrones to α,β-unsaturated sugar aldonolactones

“…The same reaction scheme applied to adduct 49 opens an easy access route to analogs of castanospermine 105 and australine 106 (Scheme 23) [19,20]. The configuration of the stereogenic centers at C-1, C-6, C-7, C-8 and C-8a of castanospermine 105 is the same as the configuration at C-6, C-2, C-1a, C-5a and C-5b of the adduct 49.…”

“…The attractiveness of cyclic dipoles as synthons in a target-oriented synthesis has been proven repeatedly [10,27,31,63]. We expected that the combination of both cyclic components should lead to a high stereoselectivity of the cycloaddition and, as depicted in Scheme 1, should also provide an attractive entry to the stereocontrolled synthesis of polyhydroxylated azabicycloalkanes with a potential bioactivity [17][18][19][20][21][22][23][24][25][26].…”

“…Amongst them, the N-benzylated derivative of 97ent is the most selective and interacts only with a-D-mannosidase [21]. In the 7-homolog of australine (108) [19] have lower activity in comparison to the native molecules. Although compound 113 has a manno-configuration on the piperidine ring, it does not exhibit any significant activity against a-Dmannosidase, but is weakly active against other enzymes [25].…”

“…However, the configuration of the stereogenic centers at C-1, C-5, C-6, C-7 and C-7a of australine 106 is different from the configuration at C-6, C-2, C-1a, C-5a and C-5b of the adduct 49 only at the stereogenic center of the C-2 carbon atom. However, bearing in mind that alkylation of the nitrogen atom, in order to form the pyrrolizidine skeleton, should proceed with an inversion of configuration, the adduct 49 represents an excellent substrate for the synthesis of 7-homoaustraline 108 [19]. Both syntheses were completed [ ( ) T D $ F I G ] to provide the expected indolizidine 107 and pyrrolizidine 108 [19,20].…”

“…Synthesis of enantiopure a,b-unsaturated lactones An unsaturated d-lactone fragment can be found in many natural products (Fig. 3), both simple such as parasorbic acid (17) [34] and osmunda lactone (18) [35], and even structurally more complex, such as anamarine (19) [36] and boronolide (20) [37]. Butenolides (unsaturated g-lactones) [38] can also be found as fragments of many natural products (Fig.…”