Total synthesis of (+)-swainsonine and (+)-8-epi-swainsonine

Abstract

Enantioselective total synthesis of (+)-swaisonine that hinges on a combination of organocatalyzed aldolization and reductive amination, affords the title compound in 9 steps, with 24% overall yield.

Synthesis of 1,4-imino-L-lyxitols modified at C-5 and their evaluation as inhibitors of GH38 α-mannosidases

“…Treatment of 15 with TBAF yielded identical alcohol 16 in good yield. As described by Trajkovic et al [ 34 ], oxidation of alcohol 16 with DMP led cleanly to the desired aldehyde 17 . As some decomposition products were formed during flash chromatography on silica gel, the sensitive aldehyde 17 was used in the next step without further purification and characterization.…”

“…Despite this fact, we did not manage the preparation of the aldehyde by the oxidation of alcohol 7 probably due to its instability [ 33 ]. However, similar aldehyde 17 bearing a Cbz protecting group instead of the benzyl moiety at the nitrogen atom was prepared as stable compound by Trajkovic et al [ 34 ]. Therefore, our attention was focused on preparation of aldehyde 17 starting from protected pyrrolidines 6 and 13 ( Scheme 3 ).…”

“…The exchange of the benzyl group in 6 and 13 for a Cbz moiety was achieved by N -debenzylation under catalytic hydrogenolysis conditions followed by protection of the liberated amines with CbzCl furnishing fully protected pyrrolidines 14 [ 35 ] and 15 . Exposure of 14 to a catalytic amount of PTSA (0.04 equiv) in a mixture of CH 2 Cl 2 /MeOH 30:1 (v/v) resulted in rapid cleavage of the trityl ether providing known alcohol 16 [ 34 ]. Treatment of 15 with TBAF yielded identical alcohol 16 in good yield.…”

Organocatalytic alkylation of carbohydrate‐containing aldehydes with dihydroquinoline N,O‐acetals: Absolute configuration of 1,2‐dihydroquinolines

“…Derivatives 5a and 5b were obtained in 57% and 66% yield, respectively. Compounds 4a and 4b are versatile reagents, which have been extensively employed for the design of biologically relevant compounds such as for instance lamellarin alkaloids, tetrahydrocarbolines, (−)‐crinipellin A, (+)‐swainsonine and (+)‐8‐episwainsonine, labystegines, and cycloalkane‐fused indoles . Final acid hydrolysis unmasked the carbonyl group, and compounds 1a and 1b have been isolated in a 40% and 64% yield, respectively, after filtration on silica gel (Scheme ).…”

On the Asymmetric Induction in Proline‐Catalyzed Aldol Reactions: Reagent‐Controlled Addition Reactions of 2,2‐Dimethyl‐1,3‐dioxane‐5‐one to Acyclic Chiral α‐Branched Aldehydes

“…Among the various ketones that can be used as the donor component for proline catalyzed cross‐aldol additions, 2,2‐dimethyl‐1,3‐dioxane‐5‐one 1 (dioxanone) occupies a prominent position as a dihydroxyacetone (DHA) equivalent and a very useful C3 building block for asymmetric synthesis , . A tactical combination of organocatalyzed aldol reaction of dioxanone 1 and reductive amination recently allowed us to synthesize optically pure iminosugars that possess common natural iminosugar's frameworks, such as members of the piperidine, pyrrolizidine, and indolizidine series. In one of these asymmetric syntheses, we used a chiral α‐substituted acceptor .…”