Glycals in Organic Synthesis: A Systematic Strategy for the Preparation of Uncommon Piperidine 1,2‐Dideoxy‐L‐azasugars and 2‐Deoxy‐1,5‐anhydro‐L‐hexitols

Abstract

A systematic synthetic strategy has been developed for producing uncommon piperidine 1,2-dideoxy-L-azasugars. This method involves the formation of open intermediates such as 2, 7, and 10 easily by ring-opening of D-glycals with aqueous mercury(II) acetate/sodium borohydride. A concise sequence of regioselective amination and cyclization reactions then allowed us to prepare the cyclic compounds 5a and 5b, L enantiomers of naturally occurring fagomine congeners such as 3-epi-fagomine (II) and 3,4-di-epi-fagomine (III), from Dglucal and D-galactal, respectively. The unnatural 3,4-di-epi-6-deoxyfagomine 9 was obtained from L-rhamnal by the

Efficient and Stereodivergent Syntheses of D‐ and L‐Fagomines and Their Analogues

“…The spectroscopic data for compounds 25a and 25b were in accordance with the literature data. [20] The removal of the benzyl ethers in 25a and 25b was carried out with Pd(OH) 2 in MeOH to afford fully deprotected -fagomine (5) and 4-epi--fagomine (6) in 80 % and 85 % yields, respectively.…”

“…However, syntheses of fagomine isomers such as 2 and 3 have been reported much more rarely. [19f] Most synthetic efforts have been directed towards the synthesis of fagomines possessing the naturally occurring  configuration; only Shipman and co-workers were able to produce the -configured fagomine diastereomer as a by-product, [18d] whereas Passacantilli and co-workers [20] reported the synthesis of 1,2-dideoxy--azasugars from -glycal derivatives.…”

Aryl Sulfonates in Inversions at Secondary Carbohydrate Hydroxyl Groups: A New and Improved Route Toward 3-Azido-3-deoxy-β-d-galactopyranosides

“…An initial study showed that the commonly used tosylate and mesylate leaving group at C3 of 4,6-O-benzylidene galactosides did not allow for inversion reactions to occur, which is not surprising as literature [9][10] reports inversions at furanose and open-chain carbohydrate secondary carbons but rarely on pyranose secondary carbons, why tuning the sulfonate leaving ability was required. Herein, we report an alternative synthetic route towards 3-azido-3-deoxy-β-D-galactopyranosides replacing labile triflates with more stable, but still sufficiently reactive, aryl sulfonates.…”