To remove an acetyl protecting group from an acetylated sugar, you typically perform a hydrolysis reaction under either basic or acidic conditions, depending on the stability of other functional groups in the molecule. Here are the common methods:

1. Basic Hydrolysis (Saponification)

Reagents:

• Sodium methoxide (NaOMe) in methanol
• Sodium hydroxide (NaOH) or potassium carbonate (K₂CO₃) in water/methanol

Mechanism: The base hydrolyzes the ester bond, releasing acetate (CH₃COO⁻) and regenerating the hydroxyl group.

Conditions:

• Room temperature to mild heating
• Reaction time: minutes to hours

Pros:

• Mild and effective
• Preserves acid-sensitive groups

Cons:

• Not suitable for base-sensitive functionalities

2. Acidic Hydrolysis

Reagents:

• Aqueous HCl or trifluoroacetic acid (TFA) in water or aqueous acetic acid

Mechanism: The acid protonates the ester, facilitating nucleophilic attack by water to cleave the acetyl group.

Conditions:

• Typically reflux or gentle heating
• Reaction time: variable

Pros:

• Good for base-sensitive systems

Cons:

• Harsh on acid-labile groups (e.g., glycosidic bonds can be cleaved)

Choosing the Method:

• Use basic conditions (e.g., NaOMe/MeOH) if your sugar has acid-sensitive groups like glycosidic bonds.
• Use acidic conditions only when base-sensitive groups (e.g., certain esters, carbonates, or enolizable ketones) are present.

Example Reaction (Base-Mediated Deacetylation):

Acetylated sugar + NaOMe in MeOH → Deacetylated sugar + CH3COONa