Question

What reagents are needed to carry out transformations [1]–[3] in the synthesis of aldehyde A? A can be converted to the antitumor agent maytansine in several steps.

Short answer

Answer

[1] Gilman Reagent

[2] ${\left({\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\right)}_4{\mathrm{N}}^{+}{\mathrm{F}}^{-},\mathrm{PCC}$

[3] Directed aldol condensation:$\mathrm{LDA},\mathrm{THF},{\mathrm{CH}}_3\mathrm{CHO},{\mathrm{H}}_2\mathrm{O}$

Step-by-step solution

Directed aldol condensation

Directed aldol condensation is a type of crossed aldol condensation where the carbonyl compound that has to form an enolate is specified. The enolate is formed using the reagent LDA.

An example of directed aldol condensation is given below:

Aldol condensation

Directed aldol condensation

The reagents [1]-[3] used in the given transformation is shown below:

The reagent [1] is a Gilman reagent, as shown below:

Reagent [1]

The reagent [2] is the set of two reagents, as shown below:

Reagent [2]

The third step is an example of directed aldol condensation, and the reagent is given below:

Reagent [3]