beta-D-Galactose pentaacetate
[CAS# 4163-60-4]

Identification

• Classification: Biochemical >> Carbohydrate >> Monosaccharide
• Name: beta-D-Galactose pentaacetate
• Synonyms: 1,2,3,4,6-Penta-O-acetyl-beta-D-galactopyranose; Penta-O-acetyl-beta-D-galactopyranose
• Molecular Formula: C₁₆H₂₂O₁₁
• Molecular Weight: 390.34
• CAS Registry Number: 4163-60-4
• EC Number: 224-008-0
• SMILES: CC(=O)OC[C@@H]1[C@@H]([C@@H]([C@H]([C@@H](O1)OC(=O)C)OC(=O)C)OC(=O)C)OC(=O)C

Properties

• Density: 1.3±0.1 g/cm³ Calc.^*
• Melting point: 143 - 144 °C (Expl.)
• Boiling point: 434.8±45.0 °C 760 mmHg (Calc.)^*
• Flash point: 188.1±28.8 °C (Calc.)^*
• Solubility: methanol: 50 mg/mL (Expl.)
• Index of refraction: 1.482 (Calc.)^*
• Alpha: 25 ° (c=10,CHCl3,on dry ba) (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319-H335
• Safety Statements: P261-P264-P264+P265-P271-P280-P302+P352-P304+P340-P305+P351+P338-P319-P321-P332+P317-P337+P317-P362+P364-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Eye irritation	Eye Irrit.	2	H319
Skin irritation	Skin Irrit.	2	H315
Specific target organ toxicity - single exposure	STOT SE	3	H335

Discovery and Applications

Beta-D-Galactose pentaacetate is the fully acetylated derivative of beta-D-galactopyranose in which the hydroxyl groups at positions 1, 2, 3, 4, and 6 are converted to acetate esters. D-galactose was identified in the nineteenth century as a product of lactose hydrolysis and was soon recognized as an aldohexose closely related to D-glucose. Detailed chemical investigations established that galactose exists predominantly in a six-membered pyranose ring form and that it displays mutarotation in aqueous solution, reflecting interconversion between alpha and beta anomers at the anomeric carbon. The isolation of distinct crystalline derivatives corresponding to these anomers provided decisive evidence for the cyclic hemiacetal structure of hexoses.

The preparation of beta-D-galactose pentaacetate emerged from systematic studies of carbohydrate acetylation. Treatment of D-galactose with acetic anhydride, typically in the presence of catalysts such as pyridine, converts all five hydroxyl groups into acetate esters. Under controlled conditions, the beta anomer of the pentaacetate can be isolated as a crystalline compound distinct from the alpha form. The availability of separate anomeric derivatives allowed chemists to measure physical properties such as melting point and optical rotation and to correlate these values with stereochemical configuration. These experimental findings were central to confirming the orientation of the anomeric substituent in the pyranose ring.

Peracetylated sugars such as beta-D-galactose pentaacetate played a critical role in classical carbohydrate chemistry before the introduction of modern spectroscopic techniques. Native monosaccharides are highly polar and often difficult to purify due to extensive hydrogen bonding and hygroscopic behavior. Conversion to acetate esters reduces intermolecular association and increases solubility in organic solvents, facilitating crystallization and handling. The improved stability and defined physical constants of the pentaacetate derivatives enabled reproducible comparisons across laboratories and strengthened structural assignments.

Beyond structural elucidation, beta-D-galactose pentaacetate has served as a protected intermediate in synthetic glycochemistry. The acetyl groups function as protecting groups that temporarily mask hydroxyl reactivity during multistep synthesis. The anomeric acetate can be activated under suitable conditions to generate a reactive intermediate capable of forming glycosidic bonds. Such reactions have been employed in the preparation of galactosides and more complex carbohydrate assemblies. After bond formation, controlled removal of acetyl groups under acidic or basic conditions restores the free hydroxyl groups, allowing further modification or yielding the target molecule.

Experimental studies of reactions involving peracetylated galactose derivatives have contributed to the understanding of stereochemical control in glycosylation. The presence of an acetyl substituent at the C-2 position influences reaction pathways through neighboring group participation, a phenomenon that has been extensively documented. Observations made using beta-D-galactose pentaacetate and related compounds have clarified how protecting groups affect reaction intermediates and product distribution, thereby informing the design of reliable synthetic strategies.

Although beta-D-galactose pentaacetate itself is primarily used as a research intermediate rather than as a commercial end product, its importance is firmly grounded in the literature of carbohydrate chemistry. Through its documented role in confirming monosaccharide structure, distinguishing anomeric configurations, and enabling controlled synthetic transformations, it exemplifies the experimentally established value of protected sugar derivatives in advancing the science of glycochemistry.

References

2021. Tobramycin-loaded complexes to prevent and disrupt Pseudomonas aeruginosa biofilms. Drug Delivery and Translational Research.
DOI: 10.1007/s13346-021-01085-3

2020. Preliminary Study for Tracing the Geographical Origin of Wheat Flour in Breads Using Stable Isotope Analysis of Wheat Proteins. Food Analytical Methods.
DOI: 10.1007/s12161-020-01866-5