Question

Propose a mechanism for the conversion of E isomer of geranyl pyrophosphate to Z isomer.

Short answer

The mechanism for the conversion of E isomer of geranyl pyrophosphate to Z isomer.

Step-by-step solution

Undergo in the presence of R-C=O-O-OH

Interconversion of double bond diastereomers can also be brought via epoxidation deoxygenating as shown below.

Nucleophilic substitution with tri-phenyl phosphine.

The nucleophilic attack by the phosphorous reagents e.g., tri-phenyl phosphine at oxirane carbon leads to aninversion of configuration and yields a charge separate intermediate.

Undergo 180-degree radiation around the C-C bond.

This undergoes elimination which requires 180-degree Celsius radiation around the C-C bond to establish the appropriate geometry.

Formation of the Z-isomer.

The bioavailability of Z-isomers is higher than that of all E-isomers during cellular absorption and transport.

Formation of the Z isomer