Synthesis of Fragments of the Capsular Polysaccharide of Haemophilus Influnzae Type B Part II. Preparation and Structural Analysis of Fragments Comprising two and Three Repeating Units

Abstract

The synthesis of spacer-containing fragments of the capsular poly-saccharide of H. influenzas, comprising two and three repeating units (9a and 9b, respectively), is presented. Ribosylribitol building blocks 1 and 2 were coupled with bis [1-benzotriazolyl]-2-chlorophenyl phosphate (3) to give the phosphotriester derivative 5a (72%), which was selectively deprotected at O-5 of the terminal ribitol residue (cleavage of the trans-1-propenyl ether) to afford compound 6a (82%). Repeated coupling of building block 2 with 6a (chain elongation), followed by propenyl- cleavage, gave analogue 6b. Both derivatives 6a and 6b were coupled with spacer 7 (chain termination). The fully protected fragments 8a (84%) and 8b (49%, starting from 6a) were thus obtained. Complete deprotection of 8a and 8b was achieved in three steps. After purification and cation-exchange, 9a and 9b were obtained in 41 and 68% yields, respectively. The structural integrity of the largest fragment (9b) was confirmed by FAB MS and various NMR spectroscopic techniques.     

High regiocontrol in the nucleophilic ring opening of 1-aralkyl-3,4-epoxypiperidines with amines—a short-step synthesis of 4-fluorobenzyltrozamicol and novel anilidopiperidines

Nucleophilic ring-opening reactions of three 1-aralkyl-3,4-epoxypiperidines with a series of aliphatic and aromatic amines have been investigated. Reactions in protic solvents, preferably 2-propanol, gave rise to 3-amino-piperidin-4-ols in ratios up to 20:1. Accordingly, 4-fluorobenzyltrozamicol, a highly potent ligand for the vesicular acetylcholine transporter was obtained directly from an epoxide ring opening in one step, without the need of chromatographic separation. Reactions in acetonitrile assisted by Li-salts, most suitable with LiBr, led regioselectively to trans-4-amino-piperidin-3-ols in high yields. N-Phenethyl substituted anilino-piperidinols as easily obtained by this method were converted into a series of new β-hydroxy substituted anilidopiperidines.     

Propagation of uncertainties and systematic errors in the measurements of long-lasting heat flows using differential scanning calorimetry

Results from the measurement of the heat of reaction of hydrothermal carbonization by power compensated differential scanning calorimetry exhibited a comparably high experimental standard deviation of around 10?C20%. The reasons for this standard deviation have been investigated and are being presented in this article. The zeroline deviation and its repeatability showed a decisive influence on the measurements due to the length of the thermal effects (several hours) and the experimental setup (high thermal capacity due to pressure capsules and hydrothermal conditions, type of calorimeter). It was quantified by reference runs and compensated mathematically. In addition, conceptual issues due to the propagation of uncertainty by sum operations are derived. There is an optimum peak length after which the uncertainty rises due to this uncertainty propagation. This optimum is at a signal level within the noise level. However, the contribution of this uncertainty showed little significance compared to the zeroline deviation and thus could be neglected. Results from hydrothermal carbonization of glucose show a mean value of 1060?J/g_daf with a standard deviation of 14% for the presented experimental setup. These values include compensations of systematic errors, including the zeroline deviation, baseline correction, leakage, and transient effects, which are discussed in detail.     

Facile preparation of Hexahydropyrrolo

Chlorolactames 2a-f reacted with sodium azide to give the cyclopropylketimines 3a-f (75-89%), and acid hydrolysis of 3c,d yielded the cyclopropylketones 6c,d (61-67%). Compounds 3a-f and 6c, d were transformed by heating (170-240 degrees C, sublimation) to the air-sensitive dihydropyrroles 4a-f (51-71%) and dihydrofurans 7c, d (85-91%). Oxidation of the dihydro derivatives 4a-f and 7c,d with DDQ led to novel types of pyrrolo[3,2-e][1,4]diazepinedione derivatives 5a-f (75-84%) and furo[1H][3,2-e][1,4]diazepinediones 8c, d (91-93%).     

Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. IV [1] Darstellung,Kristallstruktur und spektroskopische Charakterisierung von NiP4O11 und CaNiP2O7

Synthesis, Crystal Structures, and Spectroscopic Characterization of NiP₄O₁₁ and CaNiP₂O₇ From melts single crystals of NiP₄O₁₁ and CaNiP₂O₇ have been grown. These allowed refinement of the crystal structures (NiP₄O₁₁: C1¯, Z = 8, a = 12, 753(4)Å, b = 12.957(3)Å, c = 10.581(4)Å, α = 89.42(2)°, β = 116.96(2)°, γ = 90.20(2)°, R1 = 0.027, wR2 = 0.072 for 3058 I_o > 2σ (I_o), 3291 independent reflections, 290 parameters; CaNiP₂O₇: P1¯, Z = 2, a = 6.433(3)Å, b = 6.536(4)Å, c = 6.515(2)Å, α = 66.4(2)°, β = 87.5(2)°, γ = 82.7(2)°, R1 = 0.026, wR2 = 0.062 for 1624 I_o > 2σ (I_o), 2189 independent reflections, 101 parameter) and measurement of polarized electronic absorption spectra in the uv/vis/nir region (6000—32000 cm^—1). NiP₄O₁₁ is isotypic to the series of ultraphosphates MP₄O₁₁ (M = Mn, Fe, Co, Cu, Zn, Cd) that exhibit a two‐dimensional network formed from ten‐membered phosphate rings. CaNiP₂O₇ completes the series of diphosphates AMP₂O₇ (A: Ca, Sr, Ba; M = Cr — Zn) and is isotypic to CaCoP₂O₇. Ni²⁺ ions in both phosphates show distorted octahedral coordination. The electronic transitions associated with the chromophores [Ni²⁺O₆] are nicely reproduced by calculations within the framework of the angular overlap model (AOM). The parametrisation scheme leads to e_{σ, norm}(2.0Å) = 3690 cm^—1 and B = 896 cm^—1 (C/B = 4.2) for CaNiP₂O₇ and e_{σ, norm}(2.0Å) = 4150 cm^—1 and B = 948 cm^—1 (C/B = 4.5) for NiP₄O₁₁ (Δ_o(CaNiP₂O₇) = 6800 cm^—1; Δ_o(NiP₄O₁₁) = 7100 cm^—1).