Chapter 25.16, Problem 16P

Interpretation Introduction

Interpretation:

The isoprene units in crocetin, crocin, safranal, and picrocrocin are to be identified.

Concept introduction:

The isoprene unit is nothing but the carbon skeleton of isoprene without double bonds.

The isoprene ${\text{(C}}_{\text{5}}{\text{H}}_{\text{8}}\text{)}$ molecule has head and tail. The structure of isoprene $\left(\text{2-methyl-1,3-butadiene}\right)$ is shown below:

The isoprene units linked together in head-to-tail configuration. The tail of the first isoprene molecule joins with the head of the second isoprene molecule.

In higher terpenes, tail-to-tail linkage can also occur. The tail of the first isoprene molecule joins with the tail of the second isoprene molecule.

Carotenoids belong to tetrapernoids and their structure resembles with $\text{β-carotene}$.

In Caroteneoids, two $\text{C}$ units linked by the tail-to-tail fashion.

Safron is a mixture of compounds which comes from the carotenoid precursor.