From methyl mannosides to methyl octosides by a stepwise homologation with Grignard C(1) reagents
1Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44, PL-01224, Warsaw, Poland.
Abstract:
A four-step procedure for homologation of methyl alpha-D-mannofuranoside and alpha-D-mannopyranoside was examined. The reactions consisted in (i) oxidation of the terminal hydroxymethyl group in a protected sugar derivative to an aldehyde; (ii) reaction with allyloxymethylmagnesium chloride (or (phenyldimethyl)silylmethyl-magnesium chloride); (iii) protection of the newly formed secondary alcohol group; (iv) deprotection of the terminal CH(2)OR (or oxidation of the CH(2)SiMe(2)Ph) group. From methyl alpha-D-mannosides, stereoisomeric DalphaD and LalphaD methyl heptosides and from them, methyl octosides of D-threo- and L-erythro-alpha-D-manno configuration were obtained.
Related Concept Videos
Acid Halides to Alcohols: Grignard Reaction
Grignard reagents are a source of carbanions and function as nucleophiles. The mechanism begins with the nucleophilic attack by the carbanion at the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs,...
Nitriles to Ketones: Grignard Reaction
The mechanism begins with a nucleophilic attack by the Grignard reagent...
Esters to Alcohols: Grignard Reaction
The reaction requires two equivalents of the Grignard reagent and introduces two identical alkyl groups, derived from the Grignard reagent, bonded to the hydroxyl-bearing carbon of the alcohol.
The reaction follows the typical nucleophilic acyl substitution mechanism. The Grignard...
Phase II Reactions: Methylation Reactions
The mechanism of methylation unfolds in two stages. The first stage sees a methyltransferase enzyme facilitating the transfer of a methyl group from S-adenosylmethionine (SAM) to the substrate, forming S-adenosylhomocysteine (SAH). The second stage involves further metabolism of SAH into homocysteine, which can be recycled...
Preparation of Carboxylic Acids: Carboxylation of Grignard Reagents
Alcohols from Carbonyl Compounds: Grignard Reaction
Magnesium from the reagent coordinates with carbonyl oxygen, further reducing the carbonyl carbon's electron density. Thus, the carbonyl carbon is a...


