Papers by Prof. Dr. Ralf Miethchen
Acta Crystallographica Section C Crystal Structure Communications, 1995
As reported earlier [Miethchen, Rentsch & Michalik (1994). Liebigs Ann. Chem. pp. 219-222], t... more As reported earlier [Miethchen, Rentsch & Michalik (1994). Liebigs Ann. Chem. pp. 219-222], the structure of methyl 2-O-(cyclohexylcarbamoyl)-6-deoxy-3,4-O-(hexafluoroisopropylidene)-α-L-altropyranoside, C 17 H 23 F 6 NO 6 could be determined by X-ray analysis of a species which was obtained by co-crystallization with 1,1,1,7,7,7-hexafluoro-2,6-dihydroxy-2,6-bis(trifluoromethyl)-4-heptanone, C 9 H 6 F 12 O 3 , in a 2:1 molar ratio. While the pure α-L-altropyranose derivative forms needles that are not suitable for single-crystal X-ray investigations, the co-crystallization product yielded well shaped monoclinic prisms. The L-altropyranose derivative adopts a ring conformation which is intermediate between a boat and a twisted-boat conformation. The structure is stabilized by four intermolecular hydrogen bonds
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Ultrasonics Sonochemistry
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Journal of Fluorine Chemistry
ABSTRACT
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ChemInform
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ChemInform
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Synthesis Stuttgart, 2003
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Chem Commun, 2007
Twisting the silicon backbone conformation in oxygen containing oligosilanes towards dihedral ang... more Twisting the silicon backbone conformation in oxygen containing oligosilanes towards dihedral angles of 120-130 degrees either by intramolecular hydrogen bonding or incorporation into a covalently bonded ring system effectively extends the delocalization of electrons in these sigma-n mixed conjugated systems.
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J Fluorine Chem, 1991
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Carbohydrate Research, Jul 12, 2004
The attempted conversion, by treatment with CsF/TBFA in MeCN, of acetylated derivatives of 2-chlo... more The attempted conversion, by treatment with CsF/TBFA in MeCN, of acetylated derivatives of 2-chlorodifluoromethyl-2-deoxyhexopyranoses into their corresponding 2-trifluoromethyl derivatives was always accompanied by an elimination reaction. Thus, representative educts with the D-gluco- and D-manno-configuration gave derivatives of 2,3-dideoxy-2-trifluoromethyl-D-erythro-hex-2-enopyranose and 1,5-anhydro-2-deoxy-2-trifluoromethyl-d-arabino-hex-1-enitol, respectively. X-ray analyses are given for 1,3,4,6-tetra-O-acetyl-2-chlorodifluoromethyl-2-deoxy-alpha-D-mannopyranose and 4,6-di-O-acetyl-2,3-dideoxy-2-trifluoromethyl-alpha-D-erythro-hex-2-enopyranose.
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Synthesis Stuttgart, 1994
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Synthesis Stuttgart, 2005
ABSTRACT
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Eur J Inorg Chem, 1967
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Ultrasonics, 1992
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Zeitschrift für Kristallographie - New Crystal Structures, 2000
ABSTRACT
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Journal of Fluorine Chemistry, 1985
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Synthesis Stuttgart, Jul 1, 2006
ABSTRACT An efficient procedure was established to synthesize a thymidine analogue bearing an acy... more ABSTRACT An efficient procedure was established to synthesize a thymidine analogue bearing an acylsilane function at the 5'-position, starting from thymidine in four steps and 58% overall yield. This compound proved to be a valuable intermediate for the synthesis of various nucleoside analogues with a one-carbon chain elongation at the 5'-position and a useful compound towards the construction of modified oligonucleotides.
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Liebigs Annalen, 2006
ABSTRACT The 2-O-(cyclohexylcarbamoyl)-3,4-O-(2,2,2-trichloroethylidene)-protected α-altropyranos... more ABSTRACT The 2-O-(cyclohexylcarbamoyl)-3,4-O-(2,2,2-trichloroethylidene)-protected α-altropyranosyl fluorides 1, 7, and 11 were used as starting materials for intra- and intermolecular glycosylations in the presence of BF3. Because of the effective neighbouring group participation of the carbamoyl moieties, the corresponding trans-glycosides 2, 4, 6, 12, and 14 can be stereoselectively prepared from 1 and 11, respectively, in good yields. In the case of the 6-O-formyl derivative 7 the intramolecular glycosylation to 1,6-anhydro-2-O-(cyclohexylcarbamoyl)-3,4-O-(2,2,2-trichloroethylidene)-β-D-altropyranoside (8) is possible, when no other competing nucleophiles are present. Furthermore, the deoxygenation of the altrose moiety of 6-O-[6-deoxy-3,4-O-(2,2,2-trichloroethylidene)-α-l-altropyranosyl]-1,2: 3,4-di-O-isopropylidene-α-D-galactopyranose (15) in 2-position and the hydrogenolysis of the trichloroethylidene acetal protecting group were simultaneously realised. 6-O-(2,6-Dideoxy-3,4-O-ethylidene-α-l-ribo-hexopyranosyl)-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (16) was obtained by reduction of the intermediately prepared 2-xanthate of 15 with Bu3SnH/AIBN.
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Papers by Prof. Dr. Ralf Miethchen
In English: Angewandte Chemie International Edition, 1994 (2) 231 - 232.