(R)- or (S)-benzyl 4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate (7a) and (R)- or (S)-1,1-dimethylethyl 4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate (7b), readily available from serine, react with Wittig reagents to give alkenes 8. Selective deprotection followed by oxidation of the resulting unsaturated amino alcohols 9 provides vinylglycines 5 of defined configuration (> 95% ee) and double-bond geometry. D-Vinylglycines are obtained from L-serine, and conversely, D-serine gives beta,gamma-unsaturated amino acids with the L configuration. The double-bond geometry is controlled by the nature of the phosphorous ylide employed. The scope and limitations of this new methodology for the preparation of chiral vinylglycines is examined.
Synthesis and Evaluation of Sphinganine Analogues of KRN7000 and OCH
摘要:
The phytosphingosine-containing alpha-galactosylceramides (alpha-GalCers), KRN7000 and OCH, have been shown to activate NKT cells via interaction with CD1d, a member of the CD1 family of antigen presenting proteins. Evidence from KRN7000 stimulation of NKT cells suggests that alpha-GalCers may have applications in the treatment or prevention of a range of viral, bacterial, and autoimmune conditions. Moreover, OCH, a truncated analogue of KRN7000, appears to induce a T(H)2 bias, which could have implications for the treatment of autoimmune and inflammatory conditions. We have prepared the direct sphinganine-containing analogues of KRN7000 and OCH, 1 and 2, and found them to be comparable in activity to the parent compounds in inducing the release of IL-2, IL-4, and IFN gamma. In addition, compound 2 leads to a cytokine bias similar to that seen with OCH. This is significant because sphinganines are more easily accessed than phytosphingosines, which should facilitate SAR studies.