Preparation of Chiral Diphenylphosphines from D-Glucose and Enantioselective Hydrogenation with Their Rh(l) Complexes

(2R,3S)-2-Methylsulfonyloxymeihyl-3-methylsulfonyloxy-tetrahydropyran (4), derived from n-glucose, is diphenylphosphinated to (2R,3R)-2-diphenylphosphinomethyl-3-diphenylphosphino-tetrahydropyran (7), which is formed as aminor product. Compound 8 is the predominant product, formed on 3,4-elimination. Preparation and characterization of the rhodium(I) complexes 10-12 is described. Complex 10 of bidentate Iigand 7 exhibits in hydrogenation of Z-a-N-acetylaminocinnamic acid enantioselectivity comparable to that obtained with rhodium(I) complex of (-)-DIOP (-70010e. e.). Saturated monophosphine, (2S)-2-diphenylphosphinomethyl-tetrahydropyran (9) affords mixed rhodium(I) complex (11, 12), which exhibits low enantioselectivity

Syntheses of amino alcohols and chiral C-2-symmetric bisoxazolines derived from O-alkylated R-4-hydroxyphenylglycine and S-tyrosine

Chiral C-2-symmetric bisoxazolines 1b-f and 2b,c, derived from 4'-O-alkylated R-4-hydroxy-phenylglycine or S-tyrosine, were prepared. As intermediates, a series of chiral amino alcohols possessing substituted phenolic groups was prepared and fully characterized

Synthesis and Intramolecular Rearrangement of Enantiomeric Amino-alcohols in the Aliphatic Thymidine Analogues Series

The synthesis of (-)-1-(-3-amino-2-hydroxypropyl)thymine hydrochloride[(-)-(R)-(VIII)] by a catalytic hydrogenation of (-)-1-(3- -azido-2-hydroxypropyl)thymine[(-)-(S)-(VII)] is described. The resolution of (2R)- and (2S)-(3j3-acetoxy-Ls-etienamidomethyl)-2,3\u27- -dihydro-6-methyl-7H-oxazolo[3,2-a]pyrimidin-7-one[(2R)-(X) and (2S)-(X)] by fractional crystallization, followed by the hydrolysis of the resolved stereoisomers in 25% isopropanolic HCI afforded the (+) and (-) amino-alcohol hydrochlorides VIlI, respectively, The diastereoisomers X were prepared from (R,S)-2-aminomethyl- 2,3-dihydro-6-methyl-7H-oxazolo[3,2-a]pyrimidin-7-one (V) and p-nitrophenyl 3j3-acetoxy-~5-etienate (XII) by the active ester method. The conversion of X into VIlI proceeded via intramolecular formation of (5R)- and (5S)-2-(313-acetoandrost-5-en-17-yl)- -5-(thymin-1-yImethyl)oxazoline (XIII), accompanied by inversion of configuration at the asymmetric C(2) centre. The purity of the diastereoisomeric products X and XIII was determined by the 1H-NMR spectra

Preparation and Properties of Some Pro chiral and Chiral Precursors of S-3-(3-Hydroxyphenyl)-1-propylpiperidine (S-3-PPP)

Various synthetic approaches to 2,3-dehydro- and 3,4-dehydro-1-propio- nylpiperidines 12,13 and to their 1-propyl congeners 14,15,-two pairs of unsaturated, regioisomeric precursor of S-(-)-3-PPP [S-(-)-3-(3-hydroxyphe- nyl)-l-propylpyperidine, 20] were investigated. Compounds 12 and 13 were prepared by regioselective elimination of water in 11. Preparation of 14 and 15 by two different methods is described. The ratio of the E/Z isomers at the C(0)-N bond in 11-13 was determined by 13C-NMR, and separation of the enantiotopic XH-NMR signals in the enantiomers of 18 and 19 was investigated with chiral shift reagent Eu(tfc>3. Hydrogenation of 15 was performed with five different Rh(l) catalytic complexes, affording the O-methyl-conge- ner of 3-PPP 19. Complete conversion of 15 into 19 was only achieved at elevated temperature and/or pressure to give the R- or S-isomer with low enantioselectivity (7-18% e.e.)

Structural Properties of Some C2-Symmetric Schiff Bases and Stereoselectivity in Cyclopropanation of Styrene by Their Cu(I) Complexes

C2-symmetric Schiff bases derived from ñ-camphor and R-fenchone (1-6) were prepared, their configurational and conformational features determined by ID- and 2D-NMR spectra and supported by MM2 calculations. Their Cu(I) complexes prepared in situ were examined in cyclopropanation of styrene and low to medium e.e.\u27s (2-32%) were obtained. Correlation of the structure of E,E-1 and Z,Z-6 with enantioselectivity of their Cu(I) complexes revealed restricting steric requirements in the former, possessing gem dimethyl group in the proximity of the chiral centre, near to the coordination sphere of alkene and carbene, as the probable origin of its higher enantioselectivity

Structure and Relative Stability of Dirhodium Tetracamphanate Adducts with 5-Pyrido- 1,4-benzodiazepines and Their 4,5-Dihydro Congeners; First Representatives of Non-Symmetric Bidentate 1,4-Bisnitrogen Ligands

1H-NMR Spectra of dirhodium tetracamphanate adducts with 5- pyrido-1,4-benzodiazepin-2-ones 3-5 reveal different modes of com- plexation. Depending on the structure of the chelating pyridoben- zodiazepine, two types of kinetic and dynamic profiles are observed. Ligands 3 and 4, possessing a 1,4-bisnitrogen subunit with 47t electrons, behave as bidentate ligands and form the kinetically stable 1:1 adducts, non-symmetric diastereomers 6A, 7A, which undergo fast isomerization into the thermodynamically more stable 6B, 7B. Ligand 5 (4,5-dihydro derivative of 4) behaves as a pyridine derivative, forming the kinetically stable, symmetric 2:1 aduct 8, which very slowly isomer- izes into non-symetric 1:1 aduct 9. The relative stability of 8 is attributed to the hydrogen bonding N(4)-H-0(camphanyl), as well as to the low coordinating ability of the non-conjugated, pyramidal N(4) atom

Chiral Bis(tyrosinol) and Bis(p-hydroxyphenylglycinol) Oxalamide Gelators. Influence of Aromatic Groups and Hydrogen Bonding on Gelation Properties

Enantiomerically pure R,R-bis(4-hydroxyphenylglycinol) oxalamides 3 and S,S-bis(tyrosinol) oxalamides 4 were prepared and tested for their gelling properties toward organic solvents, water and aqueous mixtures with polar organic solvents. It was found that oxalamide compounds with aryl substituted phenolic hydroxy groups are efficient organogelators of highly polar solvent systems while the derivatives with free phenolic hydroxy groups tend to crystallize. The revealed different behaviour is explained on the basis of specific hydrogen bonding motifs found in the crystal structures

Heptamolybdate Ion Catalyzed Epimerization of Monosaccharides. CD Study of Binding of Monosaccharides and Polyols to Molybdate and Tungstate

Conformational properties and weak interactions of monosaccharides in the oxo-complexes with ammonium heptamolybdate (AHM) and ammonium paratungstate (APT) are studied by the CD spectroscopy, and their relation to the catalytic C(2) epimerization step is discussed. It is found for molybdate complexes that there is unequivocal correlation between the torsional angles around the 1,2,3-triol subunit in the bound monosaccharide and the Cotton effects between 325 and 300 nm, 286 and 260 nm, and that around 235 nm. A positive torsional angle in l,2-cis-2,3-cts triols leads to a positive first and second, and a negative third mentioned Cotton effect. Assuming a 1:2 ratio for the monosaccharide to Mo(VI) in the complex, as strongly indicated by a recent 95Mo-NMR study, binding in the \u27C4 conformation can be predicted for the monosaccharides from the (yxo-series, whereas for those of ribo-series binding in 4Ci conformation predominates. The first type of hexoses seems to engage the C(6)H20H group, if present, whereas the second one binds via 1,2,3-OH groups in cis-configuration. The absence of CD effects with the cyclic polyols 1—6, derived from various pyranoses, revealed that either three OH groups with cis-configuration or two cis-hydroxy groups and an axially arranged CIS-CH2OH group represent the minimal structural requirement for the formation of the CD active oxo-complexes. Two hexitols, D-glucitol 7, and D-mannitol 8, also form 1:2 complexes, engaging four hydroxy groups »from the end« of the chain (C(6)-C(3)), as found by the X ray analysis for the crystalline complex of D-mannitol. This complexation mode leaves unbound C(2), the only chiral center with the opposite configuration in these two ligands, leading to very similar CD spectra of the two complexes