Reinhard Schwesinger

An efficient homogeneous catalytic enantioselective synthesis of α-amino acid derivatives

Abstract The catalytic enantioselective alkylation of the benzophenone imine of glycine t-butyl ester is realized by an efficient homogeneous reaction with alkyl halides, the neutral, non-ionic phosphazene base (BEMP or BTPP), and chiral quaternary ammonium salts derived from thecinchona alkaloids.

Cis-trioxa-tris-β-homobenzene as tridentate ligand : X-ray crystal structure analyses of [Li(C6H6O3)2 PF6] and [Ca(C6H6O3)3H2O(ClO4)2]

Abstract In the title complexes the cis-benzenetrioxide acts as tridentate ligand, allowing for octahedral and unusual tetracapped trigonal prismatic coordination (TECTP).

Cis-trihetero-tris-σ-homobenzenes as tridentate ligands - X-ray crystal. Structure analyses of the Co(C6H9N3)2(NO3)3 and Ba(C6H6O3)4(ClO4)2-complexes

Abstract According to X-ray crystal structure analyses “cis-benzenetrisimine” ( 2 ) and “cis-benzenetrioxide” ( 1 ) act as tridentate ligands in their 2:1- and 4:1-complexes 7 (Co(C 6 H 9 N 3 ) 2 (NO 3 ) 3 ) and 8 (Ba(C 6 H 6 O 3 ) 4 (ClO 4 ) 2 ), resp. The latter is the rare example of an organic complex with the (approximate) T-symmetry.

Tert-butyl- and 2,2,2-trifluoro-1,1-diphenylethane-sulfonates -hindrance of SO-scission in SN2-substitution reactions

By application of the tert-butyl sulfonates (4a) and the 2,2,2-trifluoro-1,1-diphenylethane (TDE-) sulfonates (4b) SO-scission in SN2-substitution reactions can be drastically reduced.

Total syntheses of (−)−2-deoxyfortamines

Abstract Starting from the now readily available dianhydro-deoxy( epi )inositol (2) an efficient access to suitably protected (−)−2-deoxy-fortamines (10/11) has been worked out, in which the racemic epoxide intermediates (6) are cleanly separated via their R−(+)−1-phenylethylamine-adducts (8/9).

A versatile total synthesis of α-D-purpurosaminides C

Abstract A convenient synthesis of methyl α- D -purpurosaminide C has been developed starting from dimeric acrolein (25–30 % overall yield of each enantiomer). Key steps are the efficient separation of intermediate diastereomeric amines and the stereospecific reduction of 2-oximino-α-hexopyranosides.

A Short Novel Synthesis of the Phosphazene Base Et-P2

A novel synthesis of the phosphazene base Et-P2 is presented, which approximately halves the efforts of its production.

Zur Kristallchemie ungeladener Phosphazen-Basen, II [1] Strukturen der wasserfreien Form und zweier Hydrate des Diphosphazens (Me2N)3P=N-(Me2N)2P=NH / Crystal Chemistry of Uncharged Phosphazene Bases, II [ 1] Structures o f the Anhydrous Form and Two Hydrates of the Diphosphazene (Me2N)3P =N-(Me2N)2P=NH

The uncharged, very strong diphosphazene base (Me2N)3P=N-(Me2N)2P=NH (for short P2) and two hydrates have been characterized by crystal structure analysis. The diphosphazene. m. p. 23°C, is triclinic with space group P1̅ and Z = 2 formula units per unit cell of dimensions a = 7.595, b = 7.972, c = 14.642 Å, a = 100.19°, β = 96.15° and 7 = 100.79° at -150°C. A monohydrate, P2·H2O, m. p. 24°C, is monoclinic with P2|/c. Z = 4, a = 11.778, b = 15.415, c = 10.190 Å, and β = 93.46° at -100°C. Another hydrate, Pr 2.25 H2O. m.p. 14°C, is also monoclinic with P21/c, Z = 8, a = 10.348, b = 25.476, c = 15.791 A, and ,3 = 105.70° at -100°C. In the structure of the anhydrous diphosphazene there are no distinct intermolecular interactions. In the hydrate P2·H2O, a centrosymmetric dimer of the formula unit is formed by hydrogen bonds O-H···N arranged in a centrosymmetric four-membered ring. In the hydrate P2·2.25 H2O. hydrogen bonding O-H···O and O-H···N generates an aggregate of five fourmembered rings, alternating with a single water molecule in an unlimited chain. In spite of the high basicity of the diphosphazene, its hydrate structures are not ionic but clearly molecular.

Total syntheses of enantiomerically pure D- and L-glycosyl donors as components of sannamycin-type aminoglycoside antibiotics

Both enantiomers of purpurosaminides C (ent-7b, 13a–c), of a 2-azido analogue (ent-16b) and of 2-azido epimers (ent-26b, ent-29b), suitably protected for their direct use as glycosyl donors, are prepared from racemic 3,4-dihydro-2H-pyran-2-carbaldehyde (acrolein dimer, rac-1). The latter has been resolved on a preparative scale through the diastereoisomeric trifluoroacetylated 1′-amines obtained with (1R)- and (1S)-1-phenylethylamine, which allowed the combination of optical resolution with the introduction of the glycosyl 6-amino function.