A general and concise asymmetric synthesis of sphingosine, safingol and phytosphingosines<i>via</i>tethered aminohydroxylation
作者:Pradeep Kumar、Abhishek Dubey、Vedavati G. Puranik
DOI:10.1039/c0ob00117a
日期:——
A novel, practical and efficient enantioselective synthesis of sphingoid bases, L-threo-[2S,3S]-sphinganine (safingol), L-threo-[2S,3S]-sphingosine, L-arabino-[2R,3S,4R] and L-xylo-[2R,3S,4S]-C18-phytosphingosine is described. The synthetic strategy features the Sharpless kinetic resolution and tethered aminohydroxylation (TA) as the key steps.
l-erythrose chiron, which already contained the future C-3 and C-4 stereocentres of our target compounds. Construction of the remaining C-2 stereochemistry relied on aza-Claisen rearrangements to establish the desired vicinal aminoalcohol motif. The aliphatic chain was introduced by means of an olefin crossmetathesis process. Completion of this phytosphingolipid synthesis was then achieved through the suitable
Totalsynthesis of the natural d-ribo-phytosphingosine I and its 2-epimer III in the protected form was achieved through a common strategy. The aza-Claisen rearrangement of allylic thiocyanate (Z)-V incorporated the new stereogenic centre with nitrogen and the subsequent Wittig olefination constructed a non-polar side chain. Hydrogenation, followed by removal of protecting groups, completed the syntheses