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3.7.3.2 The Enolate [2,3]-Wittig Rearrangement

DOI: 10.1055/sos-SD-203-00213

Zeh, J.; Hiersemann, M.Science of Synthesis: Stereoselective Synthesis, (20113380.

Various π-acceptor functionalities can be used to stabilize a (formal) carbanion.[‌47‌] Carboxy groups are particularly useful because they generate Brønsted acidity at the α-proton, and the resulting enediolates have a high charge density as a result of the presence of the dianion of the carboxylic acids. The use of the enolate [2,3]-Wittig rearrangement is nicely illustrated in the total synthesis of ()-C-sulfatide (122), the C-analogue of the natural product sulfatide (Scheme 37).[‌8‌] Etherification of the α-anomer of the galactoside 134 provides the glycolate ether 135, which is treated with an excess of lithium diisopropylamide to generate an enediolate. This undergoes [2,3]-Wittig rearrangement via the transition state 136 to give an α-hydroxy acid that can be directly esterified to give the enoate 137. Subsequent hydrogenation provides the building block 138, which was used in the synthesis of ()-C-sulfatide (122).

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