D. Enders et al., DIASTEREOSELECTIVE AND ENANTIOSELECTIVE SYNTHESIS OF L-THREO-SPHINGOSINE AND D-ERYTHRO-SPHINGOSINE, Chemistry, 1(6), 1995, pp. 382-388
L-threo-sphingosine and its D-erythro isomer (1) are subunits of many
glycosphingolipids, gangliosides and ceramides. This paper describes t
he highly diastereo- and enantioselective synthesis of both isomers (d
e,ee > 98%). The key steps in the synthesis are the aldol reaction of
the SAMP hydrazone (S)-2 with racemic alpha-phenylselenylpentadecanal
3, the diastereoselective triacetoxyborohydride reduction of ketone 5
and exclusive (E) C=C double bond formation in the elimination of hydr
oxyl and selenyl moieties promoted by methanesulfonyl chloride. Mesyla
te 8 was then readily converted via the 1,3-O-acetonide-protected azid
osphingosine 9 to L-threo-sphingosine. Conversion to the known 1-O,2-N
-diacetyl-protected sphingosine 13 with subsequent Mitsunobu inversion
of the C3-OH centre afforded the D-erythro-sphingosine epimer.