Chiral vinylphosphonate and phosphonate analogues of the immunosuppressive agent FTY720.

摘要: FTY720 (2-amino-[2-(4-n-octylphenyl)ethyl]-1,3-propanediol, Fingolimod™, 1, Chart 1) is a synthetic analogue of the chiral sphingolipid myriocin (2).1 As an sphingosine, phosphorylated in vivo by sphingosine kinases, affording (S)-FTY720-phosphate (3), which activates four five known 1-phosphate (S1P, 2a) G protein-coupled receptors.2 Chart 1 Structures (1); (2); S1P (2a); and phosphate, phosphonate, (E)-vinylphosphonate analogues 3–5. Internalization subsequent polyubiquitination receptors leads to their proteasomal degradation renders cells unresponsive S1P; therefore, lymphocytes are not capable recirculation peripheral inflammatory tissues.3 Thus, has therapeutic potential, fact first receptor modulator that entered stage phase-III clinical study.4 Several syntheses 15 phosphate 3 have been accomplished.6 In contrast phosphates such as 3, phosphonate resistant action lipid phosphatases may offer improved cellular stability. A racemic mixture nonhydrolyzable (4) was reported C-O-P bond replaced with C-C-P bond;2b rac-4 found be high-affinity agonist S1P-type 1 (S1P1), similar potency (S)-3.7 We report here asymmetric FTY720, (R)-4 (S)-4. Oxazoline intermediate (S)-14 (Scheme 1), prepared modification our previous route,6c further elaborated give corresponding (S)-5. included preliminary pharmacological characterization effects these on non-transformed rat intestinal epithelial cell line IEC-6. This study revealed (S)-5, but its (R) enantiomer, exerts potent anti-apoptotic effect camptothecin (CPT)-induced apoptosis model.8 Unlike (S)-3, (S)-5 did activate S1P1 Endothelial Differentiation Gene (EDG) family receptors, making it novel enantioselective probe activating cytoprotective mechanism against induced DNA damage. Scheme 1 Synthesis from 4-bromobenzaldehyde Wittig reaction 4-bromobenzaldehyde ylide n-heptyltriphenylphosphonium bromide gave arylalkene 6 E,Z (1:3) 1). Sonogashira coupling between 4-(phenylmethoxy)-1-butyne delivered enyne 7 1:3 E:Z 92% yield. Alcohol 8 obtained reduction unsaturated bonds hydrogenolysis O-benzyl group presence Pearlman’s catalyst. After Swern oxidation provided aldehyde 9, use Mannich reagent, Eschenmoser's salt,9 afforded α-methylene 10. Reduction 10 NaBH4 CeCl3 (to suppress conjugate reduction) allyl alcohol 11.10 CeCl3, mild Lewis acid, required, since CsCl also 11 only product. Asymmetric Sharpless epoxidation11 cumene hydroperoxide (CHP) L-(+)-DIPT, Ti(OPr-i)4, molecular sieves epoxide (S)-12.12 The synthesis (S)-12 accomplished steps p-bromobenzaldehyde 46% overall Reaction trichloroacetonitrile DBU 2,3-epoxy-1-trichloroacetimidate (R)-13. tetrasubstituted carbon oxazoline 14 set up bearing desired nitrogen substituent opening (R)-13 catalytic Et2AlCl,13 74% yield for two steps. Swern 2), Horner-Wadsworth-Emmons tetramethyl methylenediphosphonate ester (S)-16 87% E/Z ratio ~10:1. Simultaneous demethylation release hydroxy amino groups treatment trimethylsilyl (TMSBr) low. Therefore, were released M HCl. amine hydrochloride neutralized (saturated aq Na2CO3), 17 converted TMSBr followed 95% methanol; 84% steps. using catalyst (S)-4. Scheme 2 Synthesis (S)-4 (S)-14 Asymmetric epoxidation D-(−)-DIPT (R)-12, via (R)-14 (R)-5 six 2). Catalytic hydrogenation 3). Scheme 3 Outline (R)-4 S1P promotes survival many types.14 Both 2a (S)-3 protect oligodendrocyte progenitor apoptotic death response growth factor withdrawal, shown pro-apoptotic cytokines microglial activation.15 ability 2a, 4 5 IEC-6 topoisomerase inhibitor CPT assessed fragmentation. Pretreatment (R)-4, or result significant fragmentation 4-h 20 µM CPT. However, we enantioselective, pretreatment showed (21 50%, respectively) CPT. In activity FTY720-phosphonate performed Ca2+ mobilization assays HTC4 stably transfected S1P1. Figure transfectants activated 76% maximal S1P-induced activation, displayed (13 ± 2 nM vs 9 (S)-3). both modest Emax values ranged 73 93% responses, EC50 increased ~2- 3-fold. 36% response, value ~5-fold 75 21 nM. Since elicit receptor, conclude mediated S1P1. Figure 1 Ca2+ dose-response relationships (2a), expressing receptor. In conclusion, described enantiomers 5. all at µM, protected apoptosis. extent CPT-induced reduced 50% 21% (S)-4, respectively. Experiments underway characterize analogues.