Additive‐Free Gold(III)‐Catalyzed Stereoselective Synthesis of 2‐Deoxyglycosides Using Phenylpropiolate Glycosides as Donors

Abstract

Stereoselective synthesis of deoxyglycosides has been achieved from benchtop stable and easily synthesizable deoxy-phenylpropiolate glycosides (D-PPGs) using gold(-III) salt as catalyst under externala dditive-free conditions. Under asimple catalytic system,D-PPGs reacted with avariety of sugar and non-sugar acceptors to produce majorly astereoselective O/N-deoxyglycosides in good to excellent yields and regenerate easily separable and reusable phenylpropiolic acid. Deoxy-PPGs containing armed and disarmed groups survived well under the optimized reaction conditions. In addition, the orthogonaln ature of D-PPGs was showcased, and 1,1'-linked trehalose-types ugar was also synthesized.[a] M.

Stereoselective Synthesis of Iminosugar 2-Deoxy(thio)glycosides from Bicyclic Iminoglycal Carbamates Promoted by Cerium(IV) Ammonium Nitrate and Cooperative Brønsted Acid-Type Organocatalysis

“…Ferrier-type allylic carbocation, followed by nucleophilic attack of the thiol at C-3 to give a transient 2,3-addition product, is favored over the 1,2-addition pathway. We reasoned that the πsymmetry of the p orbital hosting the lone electron pair in the sp 2 ). This result is in agreement with the longtime known principles of stereoelectronic control governing the condensation reactions of iminium ions.…”

“…(1R)-3,4-Di-O-acetyl-1-octylthio-5N,6O-oxomethylidene-2-deoxynojirimycin (2). Column chromatography (1:4 → 1:2 EtOAc− cyclohexane).…”

“…[α] D +44.7 (c 1.0 in DCM). 1 H NMR (500 MHz, CDCl 3 ): δ 7.28−7.18 (m, 10H, Ph), 5.05 (dd, 1H, J 1,2b = 3.7 Hz, J 1,2a = 1.8 Hz,4.89,4.58 (2d,2H,2 J H,H = 11. 6 Hz,CHPh),4.63,4.57 (2d,1H,2 J H,H = 11.4 Hz, CHPh), 4.29 (t, 1H, J 6a,6b = J 5,6a = 8.…”

“…1 H NMR (500 MHz, CDCl 3 ): δ 7.28−7.18 (m, 10H, Ph), 5.05 (dd, 1H, J 1,2b = 3.7 Hz, J 1,2a = 1.8 Hz,4.89,4.58 (2d,2H,2 J H,H = 11. 6 Hz,CHPh),4.63,4.57 (2d,1H,2 J H,H = 11.4 Hz, CHPh), 4.29 (t, 1H, J 6a,6b = J 5,6a = 8. 6 Hz, H-6a), 3.90 (m, 1H, H-3), 3.75 (dd, 1H, J 5,6b = 6.3 Hz,1H,2H, OCH 2 ), 3.24 (t, 1H, J 3,4 = J 4,5 = 9.0 Hz, H-4), 2.30 (ddd, 1H, J 2a,2b = 13.2 Hz, J 2a,3 = 4.7 Hz, H-2a), 1.54 (ddd, 1H, J 2b,3 = 11.2 Hz, H-2b), 1.47−1.43 (m, 1H, OCH 2 CH 2 ), 1.20 (m, 10H, CH 2 ), 0.81 (t, 3H, J H,H = 7.0 Hz, CH 3 ).…”

“…7 Notwithstanding, attempts to access 2deoxyiminosugar glycosides from the corresponding iminoglycal donors obstinately proceeded with concomitant double bond migration (Ferrier rearrangement) 8 to afford 2,3unsaturated compounds (Scheme 1, left panel). 9 In a previous work, we found that installing a five-membered carbamate ring in the iminosugars, thereby imparting high sp 2 hybridation character to the endocyclic nitrogen, affords bicyclic monosaccharide surrogates (sp 2 -iminosugars) that emulate both the function and chemistry of the parent carbohydrates. 10 The carbamate segment is a key integral part of the sp 2 -iminosugar glycomimetic structure, not a protecting group, which fixes the conformation about the exocyclic C-…”