Unusual 1,5-hydride shifts in Lewis acid mediated reactions of benzylated sugars. Synthesis of 3-alkylisochroman derivatives

Inhibition of Nonmammalian Glycosidases by Azetidine Iminosugars Derived from Stable 3,5-Di-O-triflates of Pentoses

“…For the synthesis of azet-DAB 3D , d -arabinose was converted to the diol 5D in three steps in an overall yield of 33% as previously described [Scheme ] . Esterification of 5D with triflic anhydride in dichloromethane in the presence of pyridine gave the stable crystalline ditriflate 6D [mp 67–68 °C; [α] D 25 +7.2 ( c 1.1, CHCl 3 )] in 95% yield.…”

Carbohydrate chiral-pool approach to four enantiomerically pure 2-naphthylmethyl 3-hydroxy-2-methylbutanoates

“…Selective tert-butyldiphenylsilylation of D-arabinose followed by isopropylidenation was performed by analogy to the known process described for L-arabinose 20,21 to furnish tert-butyldiphenylsilyl-1,2-O-isopropylidene-D-arabino-furanose 35. 43 Oxidation at the position C3 followed by Wittig methylenation furnished the olefin 36. Tebbe's reagent (m-chloro-m-methylene[bis-(cyclopentadienyl)titanium]-dimethylaluminum) could also be used, 21 but its price is rather high.…”

Recent Approaches in the Synthesis of Conformationally Restricted Nucleoside Analogues

“…Nielsen et al reported the synthesis of a conformationally restricted nucleoside analogue of the anti‐HIV drug AZT bearing a 2′,3′‐fused oxetane ring (Scheme ) 26. Treatment of the known arabinose derivative 40 27 with p ‐methoxyphenol under Mitsunobu conditions provided the corresponding ether 41 . This was oxidised to give a quantitative yield of the keto sugar 42 , which on treatment with trichloromethyl anion afforded the substituted tertiary alcohol 43 with absolute stereoselectivity.…”