- Asymmetric synthesis of unnatural amino acids and tamsulosin chiral intermediate
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An efficient and enantioselective hydrogenation of N-acetylamino phenyl acrylic acids was successfully developed by using ruthenium catalyst. This methodology is important in the field of pharmaceuticals and provides a new process for the preparation of unnatural amino acids and tamsulosin chiral intermediate.
- Arava, Veera Reddy,Amasa, Srinivasulu Reddy,Goud Bhatthula, Bharat Kumar,Kompella, Laxmi Srinivas,Matta, Venkata Prasad,Subha
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p. 2892 - 2897
(2013/09/02)
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- Asymmetric hydrogenation - Influence of the structure of carbohydrate derived catalysts on the relative enantioselectivity Q(H/Me) regarding acid and ester substrates and its inversion - Selectivity increase in water by amphiphiles
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4,6-O-Benzylidene protected 2,3-bis(O-diphenylphosphino)-D-glycopyranoside rhodium(I) chelate precatalysts 1-4 e,f showed for the hydrogenation of methyl (Z)2-N-acylamidoacrylates 6-8 a stepwise decrease of the enantioselectivity with increasing number of axially oriented hexopyranoside substituents. The decrease is even stronger for the analogous substrate acids 6h-8h resulting in an unusual low relative enantioselectivity Q = q(H)/q(Me) of 0.3 for the precatalysts 4e and 4f. Deprotected, 4,6-OH-group bearing catalysts 1-4 g,h generally show smaller differences of %ee in methanol or benzene, however, not in water. Under addition of amphiphiles a in comparison with blanks b the relative enantioselectivity Q = q(a)/q(b) clearly increases for both groups of catalysts in most cases to Q-values between 3 up to 8 - independent of a neutral or ionic nature of the amphiphile.
- Selke, Ruediger,Ohff, Manuela,Riepe, Andreas
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p. 15079 - 15102
(2007/10/03)
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- Synthesis and application of (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran as ligand for asymmetric hydrogenation of acrylic acids
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A new, chiral bisphosphine, (3R,4R)-3,4-bis(diphenylphosphino)tetrahydrofuran (4), is synthesized in three steps from (R,R)-tartaric acid esters. With rhodium(I) complexes of 4 enantiomeric excesses of 54 to 97% are obtained on catalytic hydrogenation of 2-(acetylamino)acrylic acid, 2-(acetylamino)cinnamic acids and itaconic acid. The applied substrate/catalyst ratios were between 250:1 and 11,000:1.
- Terfort
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p. 951 - 953
(2007/10/02)
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