Synthesis of Enantiopure syn-β-Amino Alcohols. A Simple Case of Chelation-Controlled Additions of Diethylzinc to α-(Dibenzylamino) Aldehydes

Abstract

Enantiomerically pure syn-2-amino alcohols 6 are prepared by addition of diethylzinc to chiral alpha-(dibenzylamino) aldehydes 4. The addition is highly stereoselective, leading to syn-2-(dibenzylamino) alcohols 5 with excellent diastereomeric excesses (76-98%). Debenzylation of 5 by hydrogenolysis on Pearlman's catalyst yields quantitatively the amino alcohols 6.

Vanadium‐Catalyzed Asymmetric Oxidation of Sulfides Using Schiff Base Ligands Derived from β‐Amino Alcohols with Two Stereogenic Centers

“…To investigate the effect of the stereochemistry of the Schiff base ligands on the enantioselectivity of the product, we also prewww.eurjoc.orgpared ligand 4 (Scheme 1), a diastereomer of ligand 3i, according to a literature method. [27] Under the same reaction conditions, ligand 4 afforded the product in moderate yield but with poor enantioselectivity ( The result indicated that syn diastereomer 3i (S,R) exerted a stronger chiral discrimination effect than anti diastereomer 4 (S,S) in the reaction. The solvent effect of the VO(acac) 2 /3i system was examined.…”

Diastereoselective Synthesis of β‐Amino‐α‐(trifluoromethyl) Alcohols from Homochiral α‐Dibenzylamino Aldehydes

“…[15] We were interested in the use of Ruppert's reagent (TMSCF 3 ) as a trifluoromethylation agent because of the mild reaction conditions that promote the addition. Thus, the reaction of homochiral dibenzylamino aldehydes 1aϪf [16] with an excess (1.5 equiv.) of TMSCF 3 and a catalytic amount of TBAF (0.05 equiv.)…”

Synthesis of Enantioenriched 2‐ and 2,6‐Substituted Piperidin‐3‐ols from α‐Dibenzylamino Aldehydes

“…Starting α-(dibenzylamino) aldehydes 1a-c were prepared as described previously. [10] The 1 H (300 MHz) and 13 C NMR (75 MHz) spectra were recorded on a Bruker AC 300 or AMX 300 spectrometer using TMS as the internal standard. IR spectra were recorded on a Perkin-Elmer Spectrum BX spectrometer as a film or KBr dispersion.…”

“…The 2-and 2,6-substituted 3-hydroxypiperidines were synthesized starting from α-dibenzylamino aldehydes 1a-c readily prepared [10] from commercially available α-amino acids. These aldehydes reacted with 4-butenylmagnesium bromide in diethyl ether at 0°C to afford the Felkin-Anh anti-2a-c amino alcohols in good yields and with excellent diastereoselectivities (Scheme 2 and Table 1).…”