Formal Total Synthesis of Salvinorin A

Area of Science:

• Organic Chemistry
• Synthetic Chemistry

Background:

• Salvinorin A is a potent kappa opioid receptor agonist with therapeutic potential.
• Efficient synthesis of salvinorin A and its analogs is crucial for pharmacological studies.

Purpose of the Study:

• To investigate the Claisen rearrangement for establishing the C9 quaternary stereocenter in salvinorin A precursors.
• To develop a scalable route to key intermediates for salvinorin A synthesis.

Main Methods:

• Preparation of an allyl alcohol intermediate from a Wieland-Miescher ketone via hydroxylation, reduction, cyanohydrin formation, and elimination.
• Two-step reduction to yield the required allyl alcohol.
• Johnson-Claisen rearrangement of the allyl alcohol to form diastereomeric unsaturated esters.

Main Results:

• The synthesis yielded an unsaturated nitrile intermediate.
• A two-step reduction successfully produced the target allyl alcohol.
• The Johnson-Claisen rearrangement afforded a mixture of diastereomeric 1,4-unsaturated esters (2.6:1 ratio).
• The major isomer was convertible to a key intermediate in the Hagiwara salvinorin A synthesis.

Conclusions:

• The Claisen rearrangement is a viable method for constructing the C9 quaternary stereocenter in salvinorin A synthesis.
• The developed route provides access to a key intermediate for the Hagiwara synthesis, facilitating further exploration of salvinorin A analogs.