591. Dealkylation and deacylation of carbohydrate derivatives with boron trichloride and boron tribromide

Abstract

The use of boron trichloride and boron tribromide is described for the deacylation and demethylation of mono-, di-, and poly-saccharide derivatives, the last two types being converted into the monosaccharide constituents.All the monosaccharides investigated are stable to the reagent, except fructose and sorbose which are both degraded to 5-hydroxymethylfurfuraldehyde.THE oxygen atoms of ethers, esters, and inany other derivatives of carbohydrates provide sites for co-ordination with electron-deficient molecules such as Lewis acids. Since some diversity of co-ordinating power can arise in a molecule through variation in polar character and steric environment of these basic oxygen centres there are clearly possibilities for effecting particular reactions at selected sites. Some initial studies with aluminium chloride were only partially successful because this reagent is difficult to separate from the products of reaction. Boron trichloride does not have this disadvantage and has proved to be a versatile reagent in carbohydrate chemistry, as has already been reported briefly-l Although it is a gas at room temperature (b. p. 12'), boron trichloride is strongly reactive at temperatures well below its boiling point and can easily be handled in a medium such as a mixture of solid carbon dioxide and acetone (ca. --80°).2 One of its valuable uses is for removal of O-methyl groups from methylated sugars which provides a rapid and

Structures of the glycopeptidolipid antigens of Mycobacterium abscessus and Mycobacterium chelonae and possible chemical basis of the serological cross-reactions in the Mycobacterium fortuitum complex

“…In addition t o these t w o latter monosaccharides, rhamnose was detected in the hydrolysis products of GPL I V . T h e absolute configuration of the sugars was determined after de-0-methylation by BC1, (Bonner et al, 1960) …”

The Identification of 3‐O‐Methyl‐l‐Rhamnose (l‐Acofriose) as Constituent of the Lipopolysaccharide of Rhodopseudomonas capsulata

“…[7] also report the migration values of all theoretically possible 6-deoxy-hexoses. The unknown 3-0-methyl-6-deoxy-hexose was therefore converted into its parent 6-deoxy-hexose by using the BC1,-technique of Bonner et al [13]. The demethylation mixture was then analyzed by borate electrophoresis.…”

Biomimetic Synthesis of (.+-.)-Galanthamine and Asymmetric Synthesis of (-)-Galanthamine Using Remote Asymmetric Induction

“…50) The use of an odorless sulfide instead of dimethyl sulfide made little difference (Table 3, Entries 3, 5). Deprotection of benzyl ethers with boron trichloride [55][56][57][58] could favorably afford in an excellent yield (95%) of 8b (Table 3, Entry 6).…”

“…[55][56][57][58] In the first strategy of transformation from 32 to (Ϫ)-1, we tried to remove the chiral imidazolidinone moiety in the early steps since the presence of a fused ring caused complexities and broadness of the NMR spectra, which interfered with structure analysis. Thus, 32 was first reduced with L-Selectride to afford allyl alcohol 33, where hydrolysis with sodium hydroxide to imine 34 via secondary amine 35 proceeded smoothly at room temperature.…”