`(+) -` Arabinose is `(2R,3S,4S) -` aldopentose. Which of the following is `(+)` arabinose ?

Options

A.
B.
C.
D.

Answer

To determine which of the given options corresponds to the `(+)` arabinose with the configuration `(2R, 3S, 4S)`, we will analyze each option step by step based on the stereochemistry rules.

### Step 1: Understanding the Configuration
We know that `(+)` arabinose is an aldopentose with the following configurations:
- Position 2: R
- Position 3: S
- Position 4: S

### Step 2: Analyzing the Options
We will analyze each option to determine the stereochemistry at positions 2, 3, and 4.

#### Option 1:
1. **Position 2**:
- Identify the groups attached to the chiral carbon.
- Assign priorities based on atomic number.
- Determine the configuration (R or S).
- Since the least priority group is on the horizontal axis, the configuration is reversed.

2. **Position 3**:
- Repeat the process of identifying groups, assigning priorities, and determining configuration.
- Again, reverse the configuration due to the least priority group being on the horizontal axis.

3. **Position 4**:
- Follow the same steps as above.

After analyzing, we find that this option does not match the required configurations.

#### Option 2:
1. **Position 2**:
- Assign priorities and determine configuration.
- Reverse the configuration due to the least priority group on the horizontal axis.

2. **Position 3**:
- Assign priorities and determine configuration.
- Reverse the configuration due to the least priority group on the horizontal axis.

3. **Position 4**:
- Assign priorities and determine configuration.
- Reverse the configuration due to the least priority group on the horizontal axis.

After analysis, we find that this option matches the required configurations `(2R, 3S, 4S)`.

#### Option 3:
1. **Position 2**:
- Follow the same steps as above.

2. **Position 3**:
- Follow the same steps as above.

3. **Position 4**:
- Follow the same steps as above.

This option does not match the required configurations.

#### Option 4:
1. **Position 2**:
- Follow the same steps as above.

2. **Position 3**:
- Follow the same steps as above.

3. **Position 4**:
- Follow the same steps as above.

This option also does not match the required configurations.

### Conclusion
After analyzing all options, we conclude that **Option 2** corresponds to `(+)` arabinose with the configuration `(2R, 3S, 4S)`.