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A Stereocontrolled, Efficient Synthetic Route to Bioactive Sphingolipids: Synthesis of Phytosphingosine and Phytoceramides from Unsaturated Ester Precursors via Cyclic Sulfate Intermediates

2000; American Chemical Society; Volume: 65; Issue: 22 Linguagem: Inglês

10.1021/jo001225v

1520-6904

Linli He, Hoe‐Sup Byun, Robert Bittman,

Polysaccharides and Plant Cell Walls

An efficient and highly enantioselective method for the preparation of d-ribo- and l-lyxo-phytosphingosines (1a,b, respectively) and phytoceramides (2a,b) has been developed. The key steps in the syntheses are as follows: (i) osmium-catalyzed asymmetric dihydroxylation of 4-O-protected (E)-α,β-unsaturated ester 5 (generated by dihydroxylation of 1-hexadecene, followed by oxidation to the aldehyde and Horner−Wadsworth−Emmons olefination), (ii) conversion to cyclic sulfate intermediate 7, and (iii) regioselective α-azidation of 7. Reduction of 4-O-protected 2-azido ester 8 via α-azidolactone 9 afforded phytosphingosine 1a. Staudinger reduction of the azido group of 8, followed by in situ N-acylation in aqueous media and reduction of the ester functionality with NaBH4/LiBr, provided phytoceramide 2a. By using a similar approach, phytosphingosine 1b was synthesized. d-erythro-4,5-Dihydrosphingosine 1c and d-erythro-4,5-dihydroceramide 2c were synthesized in high yield from 1-hexadecanol via cyclic sulfate intermediate 15. The desired configurations at C-2, C-3, and C-4 of the sphingoid chain can be accessed readily by the route described here.