A C2‑Symmetric Chiral Pool-Based Flexible Strategy: Synthesis of (+)- and (−)-Shikimic Acids, (+)- and (−)-4-epi-Shikimic Acids, and (+)- and (−)-Pinitol
journal contributionposted on 04.04.2014, 00:00 by Bakthavachalam Ananthan, Wan-Chun Chang, Jhe-Sain Lin, Pin-Hui Li, Tu-Hsin Yan
Via combination of a novel acid-promoted rearrangement of acetal functionality with the controlled installation of the epoxide unit to create the pivotal epoxide intermediates in enantiomerically pure form, a simple, concise, flexible, and readily scalable enantiodivergent synthesis of (+)- and (−)-shikimic acids and (+)- and (−)-4-epi-shikimic acids has emerged. This simple strategy not only provides an efficient approach to shikimic acids but also can readily be adopted for the synthesis of (+)- and (−)-pinitols. These concise total syntheses exemplify the use of pivotal allylic epoxide 14 and its enantiomer ent-14. A readily available inexpensive C2-symmetric l-tartaric acid (7) served as key precursor. In general, the strategy here provides a neat example of the use of a four-carbon chiron and offers a good account of the synthesis of functionalized cyclohexane targets.