✍ Scribed by Dipl.-Chem. Monika H. Schmitt; Prof. Dr. Siegfried Blechert
No coin nor oath required. For personal study only.
ing stages, any diastereoisomer contamination of 6 a or 6b would be apparent from an examination of the camphanate methyl resonances in the 'H NMR spectra. At no stage was any such contamination seen. A two-step deprotection strategy involving removal of the benzyl protecting groups on phosphates by hydrogenolysis and then cleavage of camphanate esters in a concentrated solution of ammonia at 60 "C was effective with no migration of phosphate groups." 'I Tetrakis(ph0sphate)s 2 a and 2b could then be isolated on a gram scale as the cyclohexyl-ammoniumr7a1 or potassium[7d1 salts in overall yields of 60-70% from 4 a and 4 b. The structures of 2 a and 2 b were confirmed by 'H, 13C, and 31P NMR spectroscopy as well as high-resolution FAB-MS. We recently used bulk material prepared in this fashion to investigate the submolecular acid-base properties of Ins(1,3,4,5)P4 by 31P NMR titration experiments.
["] Alternatively, ion-exchange chromatography on Q-Sepharose Fast-Flow gave the pure tetrakisphosphates as their triethylammonium salts. A sample of 2a was identical to biologically-derived ~-Ins(1,3,4,5)P, with respect to its interaction with GAPl'P4BP.
In conclusion, we describe rapid access to pure synthetic D-and L-Ins( 1 ,3,4,5)P4 from readily available starting materials by simultaneously using camphanate esters as desymmetrizing auxiliaries and protecting groups. This strategy should have wider applicability in the inositol phosphate field. Furthermore, the technique is capable of providing D-InS(l ,3,4,5)P4 in quantities that will now be required for crystallographic and NMR studies of its interaction with the rapidly expanding range of Ins(1 ,3,4,5)P4-binding proteins.
4a, b: To a stirred suspension of 3 (2.00 g, 10.5 mmol) in dry CH,CI, (40 mL) at 0 "C were added Et3N (3.3 mL, 23.7 mmol) and a catalytic amount of 4-dimethylaminopyridine (80 mg). A solution of (1s)-( -1-camphanic acid chloride (4.55 g, 21.0 mmol) in dry CH,CI, (10 mL) was added dropwise under an N, atmosphere at 0 "C. The cooling bath was removed after 30 min, and stirring continued for a further 30 min. After this time almost no solid remained, and TLC (CH,Cl,/ethyl acetate 3/1) showed two major products at Rf = 0.32 and 0.23. The solvents were removed in vacuo, and the residue was purified by flash chromatography (CH,CI,/ ethylacetate4/1) togive first 4a(3.46 g, 6.28 mmol, 60% yield)and then4b (1.35 g, 2.45 mmol, 23 % yield).
PdjC under an atmosphere of H, at room temperature overnight. The catalyst was removed by filtration, and the solvents in vacuo. The residue was dissolved in a concentrated solution of aq ammonia, and the solution stirred at 60'C in a sealed Pyrex autoclavable bottle for 6 h. The solution was allowed to cool and then concentrated under reduced pressure. The residue was dissolved in deionized water, and the camphanamide removed by washing with CH,CI, (3 x ) followed by Et,O. Purification by ion-exchange chromatography on Q-Sepharose Fast-Flow eluting with a gradient of triethylammonium bicarbonate buffer (pH 8, 0-1 M) gave the pure triethylammonium salts of 2a or 2b, which eluted at 730-850 mM buffer. For larger-scale production treatment with Dowex 50 H + resin gave solutions of the free acids of 2 a or 2b, which were washed again with CH,C1, and Et,O, and then converted into either the cyclohexylammonium [7a] or potassium [7d] salts in quantitative yield from 6 a or 6b.
📜 SIMILAR VOLUMES
## Abstract Annelated pentafulvenes 2, 10, 13, and 14 are efficiently accessible by a palladium‐catalyzed domino coupling process of aryl substituted vinylic bromides 1, 9, 11, and 12, 5‐Membered palladacycles 3 are discussed as key intermediates.