Q.29-56 - Organic Chemistry (Mcmurry)

Question

In step 8 of fatty-acid biosynthesis (Figure 29-5), reduction of transcrotonyl ACP gives butyryl ACP. A hydride from NADPH adds to C3 ofthe crotonyl group from the Re face, and protonation on C2 occurs onthe Si face. Is the reduction a syn addition or an anti addition?

Step-by-Step Solution

Answer

The reduction of syn addition or an anti-addition can be explained.

Addition is stereo chemically syn

In step 8, there is an oxidation of fatty acids which involves the reduction of the carbon double bond of carbonyl ACP by NADPH for the yield of butynyl ACP. The addition is stereo chemically syn and addition of H anhydride with the addition of 2 carbon. They are syn with each other.

Diagrammatic representation

The diagram can be drawn as,

The reaction proves the stereo chemistry for reduction in step 8 of the fatty acids oxidation. There is a reduction in syn addition in vertebrates whereas other organisms will carry chemistry with different stereochemistry.