Synthesis of sphingosines, 11. Convenient synthesis of phytosphingosine and sphinganine fromD-galactal andD-arabitol
✍ Scribed by Wild, Robert ;Schmidt, Richard R.
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 988 KB
- Volume
- 1995
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Phytosphingosine 1 Sphinganine I Galactal I 2-Deoxy-~-galactose I D-Arabitol I Carbohydrates 3,4,6-Tri-O-benzyl-~-galactal (3) was directly converted into 3,4,6-tri-O-benzyl-2-deoxy-~-galactose (5).
Wittig reaction of 5 with alkyltriphenylphosphonium salts in the presence of nbutyllithium as the base afforded olefins 6a, b which could be readily transformed into phytosphingosines l a , b via different routes: (i) at first azido group introduction and then double bond and protective group removal, and azido group generation via hydrogenation; (ii) 2-0-mesylation, then double bond and benzyl group removal via hydrogenation, and finally nitrogen introduction; (iii) selective double bond hydrogenation, then nitrogen introduction, and finally benzyl group removal and amino group generation via hydrogenation. Wittig reaction of 5 with alkyltriphenylphosphonium salt in the presence of potassium tert-butoxide as the base afforded diene 7a which proved to be a convenient precursor for sphinganine syntheses; thus, 2-O-mesylation, then double bond and benzyl group removal via hydrogenation and 1,3-O-acetylation, and finally nitrogen introduction and de-0-acetylation afforded 23a. Based on the convenient transformation of D-arabitol into the 1,3-O-benzylidene derivative 25 a further phytosphingosine synthesis is outlined. Sphingosine, phytosphingosine, and sphinganine (a metabolic precursor of sphingosine and phytosphingosine) are long-chain amino alcohols with generally 18 or 20 carbon atoms; they are building blocks for sphingolipids (sphingomyelin, glycosphingolip-ids, and some glycosylphosphatidylinositol anchors of proteins) which are important membrane constituentsr2]. Phytosphingosine (Scheme 1, 1) was first detected in plantd4], yeasd5], and other Thus, it was found that its occurrence is