Divergent total synthesis of d-ribo-phytosphingosine and l-ribo-phytosphingosine from d-ribose

Divergent total synthesis of d-ribo-phytosphingosine (1) and l-ribo-phytosphingosine (2) was achieved from readily available d-ribose via cross-metathesis reaction, Wittig reaction, and diastereoselective amination reaction of allylic ethers using chlorosulfonyl isocyanate (CSI) as the key steps. As results, reactions of anti-1,2-dibenzyl ethers 11 and 16 with chlorosulfonyl isocyanate afforded exclusively anti-1,2-amino alcohols 12 and 17 with diastereoselectivity of 32:1 and 31:1 in 75% and 76% yields, respectively. These results could be explained by the neighboring group effect, leading to retention of stereochemistry.