Synthesis of hydroxylated pyrrolidines by allenic cyclisation
作者:Pearly Shuyi Ng、Roderick W. Bates
DOI:10.1016/j.tet.2016.08.029
日期:2016.10
The diastereoselective gold(I) catalysed cyclisation of highly substituted aminoallene derivatives allows the synthesis of both epi-DAB-1 and di-epi-lentiginosine. While the sense of stereoselectivity observed is in line with earlier observations on analogous piperidine-forming cyclisations, different ligands and reaction conditions are required to obtain good yields.
Synthesis of (−)-lentiginosine, its 8a-epimer and dihydroxylated pyrrolizidine alkaloid from d-glucose
作者:Vinod D. Chaudhari、K.S. Ajish Kumar、Dilip D. Dhavale
DOI:10.1016/j.tet.2006.02.074
日期:2006.5
intramolecular conjugate addition reaction leading to the formation of dihydroxypyrrolidine-ester 6a and monohydroxypyrrolidine-γ-lactone 6b. Intermediates 6a and 6b were efficiently converted to (−)-lentiginosine 3a, its 8a-epimer 3b, and pyrrolizidine azasugar 4 in good overall yield.
Synthesis of pyrrolidine iminosugars, (−)-lentiginosine, (−)-swainsonine and their 8a-epimers from d-glycals
作者:Alafia A. Ansari、Y. D. Vankar
DOI:10.1039/c3ra47555g
日期:——
Synthesis of pyrrolidine iminosugars has been described from D-glycals via dihydroxylation, oxidative cleavage and double nucleophilic displacement as the key steps. The pyrrolidines obtained have been utilized for the synthesis of important bicyclic iminosugars, viz. (−)-lentiginosine and (−)-swainsonine and their 8a-epimers, which are known to be glycosidase inhibitors.
unprotected pyridinium-polyol unit using Mitsunobu methodology. Subsequent PtO2-catalyzed diastereoselective hydrogenation of the pyridinium ring proceeded smoothly and led to the expected dihydroxyindolizidines with excellent yields. This stereochemically flexible strategy has been illustrated by the concise total synthesis of non-natural products derivatives such as (−)-lentiginosine and its stereoisomers
A redox-neutral alpha-C-H oxygenation of commercially available pyrrolidin-3-ol with a monoprotected p-quinone generated an N-aryliminium ion intermediate, which reacted in situ with boronic acid nucleophiles to produce a series of cis-2-substituted pyrrolidin-3-ols. With this strategy, 8-epi-(-)-lentiginosine was synthesized from (3R,4R)-pyrrolidine-3,4-diol in three steps.