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Homochiral oxazolidin-2-ones and imidazolidin-2-ones by tandem nucleophilic addition-conjugate addition
No full textTreatment of both primary alcohols 1a,b and secondary amines 1c,d, tethered to a Michael acceptor with (R)-phenylethyl isocyanate in the presence of DBU gave in good yield and high stereoselection diastereomeric mixtures of oxazolidin-2-ones 2a,b and 3a.b and imidazolidin-2-ones 2c,d and 3c,d, respectively. The cyclisation reaction Was Studied computationally by ab initio quantum mechanical methods. The observed stereoselectivity was explained on the basis of the different stability of both anions and transition states leading to 2a and 3a, respectively. The usefulness of the method was proven by conversion of 2a into the enantiomerically Pure bioactive amino acid
Conformationally restricted analogues of both (S)-B-homoserine and (S)-aspartic acid from chiral 3-acylamino pyrrolidin-2-ones
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Regio- and Stereoselective Synthesis of Methyl α-L-Daunosaminide Hydrochloride
No full textMethyl 4-O-(trichloroacetamidoyl)-2, 3, 6-trideoxy-α-L-threo-hex-2-enopyranoside (6), prepared from methyl 2, 3, 6-trideoxy-α-L-threo-hex-2-enopyranoside (5), was cyclized to the iodooxazoline 7 which, by hydrolysis under acidic conditions, afforded the corresponding hydrochloride 8. The deiodination reaction was performed with Bu3SnH and methyl 3-amino-2, 3, 6-trideoxy-α-L-lyxopyranoside hydrochloride (methyl α-L-daunosaminide hydrochloride) 1 was obtained in 80% yield. The intermediate 5 was synthesizedstarting from methyl 4-O-mesyl-2, 3, 6-trideoxy-α-L-erythro-hex-2-enopyranoside 3 in 80% yield by means of carbonate anion on polymeric support. © 1984, American Chemical Society. All rights reserved
Stereoselective approach to both 3,4-trans-disubstituted pyrrolidin-2-ones and pyrrolidines.
No full texta-methylene-b-trichloroacetylamino alkanoates from trichloroacetimidates of the Baylis-Hillman adducts
No full textCyclisation of (R)- and (S)-N-allyl-N-(1-phenylethyl) methoxycarbonylacetamide mediated by Mn(III): Preparation and structural assignment of 3-aza-2-oxobicyclo[3.1.0]hexanes
No full textQuaternary centres: a tool for modulating foldamer conformations?
No full textFoldamers, 6-8 ottobre 2010, Bologn
Steric constraints against [3,3]-sigmatropic rearrangement of allylic azides. A convenient approach to Î2-L-4-aminopent-2-enoglyceropyranosides
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