Allyl 4,6-O-benzylidene-1-β-D-glucopyranoside

Allyl 4,6-O-benzylidene-1-β-D-glucopyranoside

Allyl 4,6-O-benzylidene-1-β-D-glucopyranoside is a protected carbohydrate derivative used as a key intermediate in stereoselective glycosylation and oligosaccharide synthesis. Its structure combines an allyl group at the anomeric position with a benzylidene acetal protecting the 4,6-hydroxyl groups, enabling precise functionalization of the glucopyranoside ring.

Chemical Identity

• Molecular Formula: C₁₆H₂₀O₆
• Molecular Weight: 308.32 g/mol
• Protection Groups: Benzylidene acetal (4,6-O), allyl ether (anomeric position)

Synthesis

The compound is synthesized from 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide via mercury-mediated allylation, followed by benzylidene acetal formation. Key steps include:

1. Regioselective Protection: THF solvent promotes C-2 benzylation in α-anomers, while β-anomers (like this compound) form stable intermediates due to reduced steric hindrance.
2. Crystallization: Purification often avoids chromatography, leveraging crystallization from solvents like methanol.

Structural Features

• Benzylidene Acetal: Locks the 4,6-hydroxyls in a rigid bicyclic structure, leaving 2- and 3-positions reactive for further modifications.
• Allyl Group: Enhances stability and serves as a glycosyl donor in coupling reactions. The β-configuration at the anomeric center ensures stereochemical control during glycosidic bond formation.

Applications

• Glycosylation: Used in TMSOTf-mediated reactions to construct α-linked disaccharides (e.g., α-D-Gal-(1→2)-D-Glc) with high stereoselectivity.
• Intermediate for Glycolipids: Derivatives like 2-O-allyl-3,4,6-tri-O-benzyl-D-glucopyranose are precursors for bacterial membrane glycolipids.
• Chiral Building Block: Facilitates synthesis of complex sugars and pharmaceutical intermediates.

Reactivity and Functionalization

• The allyl group can undergo ozonolysis or hydrogenation for deprotection.
• Selective deprotection of the benzylidene acetal (e.g., using acidic conditions) regenerates 4,6-hydroxyls for further derivatization

This compound’s strategic protection pattern and stereochemical integrity make it invaluable in carbohydrate chemistry for targeted synthesis of bioactive molecules.

Citations:

1. https://www.beilstein-journals.org/bjoc/articles/3/26
2. https://www.chemicalbook.com/ChemicalProductProperty_EN_CB7209242.htm
3. https://www.taylorfrancis.com/chapters/synthesis-4-6-benzylidene-acetals-methyl-glucopyranoside-ethyl-1-thio-gluco-galactopyranoside-gijsbert-van-der-marel-jeroen-codee/10.1201/b16602-26
4. https://pubchem.ncbi.nlm.nih.gov/compound/4_6-O-Benzylidene-D-glucopyranose
5. https://pubmed.ncbi.nlm.nih.gov/963695/
6. https://pubmed.ncbi.nlm.nih.gov/21550022/