Show how each of the following compounds can be prepared from the given starting material. In each case, you will need to use a protecting group.
a.
b.

Verified step by step guidance

1. Step 1: Analyze the starting material and the target compound. The starting material contains a hydroxyl group (-OH) and an ester functional group. The target compound introduces a new hydroxyl group at a specific position, requiring selective reactivity.
2. Step 2: Protect the existing hydroxyl group in the starting material to prevent unwanted reactions. Use a protecting group such as a silyl ether (e.g., TBDMS-Cl) to temporarily mask the hydroxyl group.
3. Step 3: Perform the desired reaction to introduce the new hydroxyl group. This can be achieved through a selective reduction of the ester group using a reducing agent like DIBAL-H (Diisobutylaluminum hydride) to form an aldehyde intermediate, followed by further reduction to an alcohol using NaBH4 or LiAlH4.
4. Step 4: Remove the protecting group from the original hydroxyl group to restore its functionality. Use a mild acid or fluoride source (e.g., TBAF for silyl ethers) to deprotect the hydroxyl group.
5. Step 5: Verify the structure of the final compound to ensure it matches the target compound. Confirm that both hydroxyl groups are correctly positioned and the ester group has been converted to the desired alcohol.

Key Concepts

Protecting Groups

Protecting groups are temporary modifications used in organic synthesis to prevent certain functional groups from reacting during a chemical reaction. They allow chemists to selectively modify other parts of a molecule without interference. After the desired reaction is completed, the protecting group can be removed to restore the original functional group.

Silyl Ethers

Silyl ethers are a class of protecting groups derived from silanes, commonly used to protect alcohols during chemical reactions. They are stable under a variety of reaction conditions and can be easily removed by hydrolysis or fluoride treatment. This makes them particularly useful in multi-step synthesis where selective reactivity is required.

Functional Group Interconversion

Functional group interconversion refers to the process of transforming one functional group into another through chemical reactions. This concept is crucial in organic synthesis as it allows chemists to create desired compounds by modifying existing structures. Understanding the reactivity and compatibility of different functional groups is essential for successful synthesis.