A stereoselective synthesis of d-erythro-spingosine

New approaches to synthesis of stereospecific sphingomyelin

Enormous progress in the asymmetric synthesis of stereochemically and chemically pure D-erythro-sphingosine and ceramides led to the development of a practical, efficient, easily scaleable process to provide industrial quantities of chiral sphingosine and ceramides. This established a new platform of chiral starting materials which facilitate the synthesis of complex sphingolipids. Utilizing stereochemically homogeneous, fully synthetic ceramides, two efficient synthetic methods were developed for the preparation of ultra pure stereochemically homogeneous sphingomyelins. The first method adapted highly efficient phosphoramidite technology from oligonucleotide chemistry. This method allows selective insertion of a phosphocholine moiety into 3-O-protected ceramide through phosphitylation, followed by choline attachment, phosphite oxidation and deprotection. This route provides stereochemically homogeneous sphingomyelin in 35-79% yield. The second route is based on the reaction of selectively protected ceramides with cyclic chlorophosphate followed by treatment with trimethylamine to give the desired sphingomyelins in 50% yield. Multigram quantities of 14C-labeled N-palmitoyl-D-erythro-sphingomyelin were produced with specific activity > 1000 dpm/nmol.

Chemoenzymatic Synthesis of All Four Stereoisomers of Sphingosine from Chlorobenzene: Glycosphingolipid Precursors(1)(a)

Advantageous use of homochiral cyclohexadiene-cis-1,2-diol 2, available by means of biocatalytic oxidation of chlorobenzene with toluene dioxygenase, has enabled the synthesis of all four enantiomerically pure C(18)-sphingosines 1. The four requisite diastereomers of azido alcohols 4a-d were accessed by regioselective opening of epoxides 7 and 8 with either azide or halide ions. The configuration of C4 and C5 in azides 4 defines the stereochemistry of the incipient sphingosine chain, liberated from 4 by the oxidative cleavage of the C1-C6 olefin. For L-threo-sphingosine (1b), lactol 20b generated by this cleavage was converted by periodate oxidation to azido deoxy L-threose 22b, which gave 1b upon Wittig olefination and reduction. Similarly, D-erythro-sphingosine (1a) and L-erythro-sphingosine (1c) were generated from 4a,c, respectively. The last sphingosine (1d) was synthesized from the silyl-protected azido alcohol 29d. Subsequent transformations provided silyl-protected azido deoxy D-threose 32d, which upon Wittig olefination and reduction gave D-threo-sphingosine (1d). Experimental and spectral data are provided for all new compounds.

An efficient, stereoselective synthesis of 4-E- and 4-Z-D-erythro-sphingenine and related compounds from 2-amino-2-deoxy-D-glucose

Efficient, stereoselective synthesis of 4-E- and 4-Z-D-erythro-sphingenines having C16, C18, and C20 carbon-chains was achieved in 13 steps, starting from allyl 2-benzyloxycarbonylamino-2-deoxy-alpha-D-glucopyranoside. 2-Amino-1,6-di-O-tert- butyldiphenylsilyl-2-N,3-O-carbonyl-2-deoxy-D -allitol was used as the key intermediate.