CONVENIENT SYNTHESIS OF PHYTOSPHINGOSINE AND SPHINGANINE FROM D-GALACTAL AND D-ARABITOL

3,4,6-Tri-O-benzyl-D-galactal (3) was directly converted into 3,4,6-tr i-O-benzyl-2-deoxy-D-galactose (5). Wittig reaction of 5 with alkyltri phenylphosphonium salts in the presence of n-butyllithium as the base afforded olefins 6a, b which could be readily transformed into phytosp hingosines 1a, b via different routes: (i) at first azido group introd uction and then double bond and protective group removal, and azido gr oup generation via hydrogenation; (ii) 2-O-mesylation, then double bon d and benzyl group removal via hydrogenation, and finally nitrogen int roduction; (iii) selective double bond hydrogenation, then nitrogen in troduction, and finally benzyl group removal and amino group generatio n via hydrogenation. Wittig reaction of 5 with alkyltriphenylphosphoni um salt in the presence of potassium teri-butoxide as the base afforde d diene 7a which proved to be a convenient precursor for sphinganine s yntheses; thus, 2-O-mesylation, then double bond and benzyl group remo val via hydrogenation and 1,3-O-acetylation, and finally nitrogen intr oduction and de-O-acetylation afforded 23a. Based on the convenient tr ansformation of D-arabitol into the 1,3-O-benzylidene derivative 25 a further phytosphingosine synthesis is outlined.