Q20P - Organic Chemistry (Mcmurry)

Question

Assign R or S stereochemistry to the two chirality centers in isocitrate, and tell whether OH and H add to the Si face or the Re face of the double bond.

Step-by-Step Solution

Answer

                                         H group adds at the Re face of the carbon group

Step1: Citric acid cycle

The water can be added reversibly to the -unsaturated carbonyl compounds to give -hydroxyl carbonyl compounds. An addition that is related to a  -unsaturated carboxylic acid occurs in a biological way such as the citric acid cycle of food metabolism, where cis-aconitate is converted into isocitrate by the conjugate addition of the water to a double bond.

Step 2: Stereochemistry

The stereochemistry of the two chiral centers in isocitrate is (2S,3R). The -OH group adds to the Re face of the carbon group. The H group adds at the Re face of the carbon group which is as shown:

                                            H group adds at the Re face of the carbon group