A method for the selective reduction of carbohydrate 4,6-O-benzylidene acetals

Glycopeptide Synthesis through endo‐Glycosidase‐Catalyzed Oligosaccharide Transfer of Sugar Oxazolines: Probing Substrate Structural Requirement

“…Selective reductive ring-opening of the benzylidene group in 15 by treatment with Et 3 SiH/TFA/trifluoroacetic anhydride/ CH 2 Cl 2 [24] gave compound 18, with a benzyl group attached to the 6'-O-position. The benzoyl groups were then replaced by acetyl groups to give compound 19.…”

TMSOTf‐Catalyzed Silylation: Streamlined Regioselective One‐Pot Protection and Acetylation of Carbohydrates

“…The fully orthogonally protected building blocks 22a and 22b were furnished in good yields after the TMSOTf-catalytic cycles were extended to acylation [step (e)]. [19] Further regioselective reductive O4-or O6-benzylidene ring-opening of the fully protected intermediates 22a and 22b in the same pot by use of trifluoroacetic acid/Et 3 SiH [20] or TMSOTf/BH 3 ·THF [21] [steps (f) or (g)] gave the corresponding 4-alcohols 23a and 23b or 6-alcohols 24a and 24b in good yields even after five consecutive reactions in one-pot fashion. After O4,O6-benzylidenation and TBAF treatment to form the 2,3-diol intermediates in situ, the 3-alcohols 25a and 25b were obtained from 1a and 1b, respectively, through regioselective O2-benzoylation [22] in good yields.…”

Characterization of the LM5 pectic galactan epitope with synthetic analogues of β-1,4-d-galactotetraose

“…Regioselective opening of the benzylidene acetal of 21 proved challenging. No conversion was observed upon treatment with NaCNBH 3 /HCl [24] or NaCNBH 3 /I 2 [25] , whereas Et 3 SiH/TFA [21] and Et 3 SiH/Cu(OTf) 2 [26] only resulted in slow hydrolysis. Instead, the acetal was hydrolyzed with ethanethiol and ptoluenesulfonic acid (p-TSA) followed by a selective acetylation of C6-OH to yield 22 (Scheme 4).…”

“…Acceptor 19 was obtained from 10 by regioselective opening of the benzylidene acetal with triethylsilane/trifluoroacetic acid (Et 3 SiH/TFA) in 80%. [21] The regioselectivity was validated by acetylating the liberated C4-OH, which resulted in a characteristic downfield shift from 3.98 ppm to 5.08 ppm of the H-4 proton in the NMR spectrum, whereas the H-6 protons resonated at the same frequencies as for the starting material. [22,23] Trimethylsilyl trifluoromethanesulfonate (TMSOTf) catalyzed coupling of donor 18 and acceptor 19 afforded disaccharide 20 in an excellent yield of 81% (Scheme 4).…”