Hence the molecule is

Sometimes, the determination of configuration of a compound drawn as a Fischer projection is necessary. The rules are given below.

• Rank the groups (or atoms) that are bonded to the asymmetric carbon in order of priority.
• Draw an arrow from the group (or atom) with the highest priority (1) to the group (or atom) with the next highest priority (2). If the arrow points clockwise, the enantiomer has the R configuration; if it points anti-clockwise, the enantiomer has the S configuration, provided that the group with the lowest priority (4) is on a vertical bond.

• If the group (or atom) with the lowest priority is on a horizontal bond, the answer you get from the direction of the arrow will be the opposite of the correct answer. For example, if the arrow points clockwise, suggesting that the asymmetric carbon has the R configuration, it actually has the S configuration; if the arrow points counter clockwise, suggesting that the asymmetric carbon has the S configuration, it actually has the R configuration. In the following example, the group with the lowest priority is on a horizontal bond, so clockwise signifies the S configuration, not the R configuration.