[OrganicBanana]

Hello, I am stuck on a step in my total synthesis on how to preform an enantioselective thiol addition of β-mercaptolactate to α,β-unsaturated Dehydrocurvularin species at the four position with R configuration. Thank you for your time.

[discodermolide]

Try an organocatalytic reaction with proline or the like as a chiral base.
Plenty of literature out there for this sort of reaction.