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This round of synthesis golf concerns the Corey synthesis of Erythronolide B (J. Am. Chem. Soc. 1978, 100 (14), 4620–4622).
In order to narrow the scope of the challenge, only a small fragment of the natural product will be considered. Fragment 2 was an intermediate on the Corey route, and provided C10-C13 of Erythronolide B.
Crucially, 2 was needed as a single enantiomer and diastereomer. In the original Corey report, 13 steps were needed to accomplish the synthesis of the fragment, a length which prevented significant amounts of material from being made.
The challenge is to propose a synthesis of 2 which sets up the required 1,2-stereochemistry with absolute configuration. You may start from anything commercially available in the Sigma–Aldrich catalogue, including chiral building blocks.