Memory of chirality in the electrochemical oxidation of N-o phenylbenzoylated prolinols

Heterocycles

Volumn 79, Issue C, 2009, Pages 339-345

  Wanyoike, George Ng'aNg'a ^a   Matsumura, Yoshihiro ^a   Onomura, Osamu ^a  

^a NAGASAKI UNIVERSITY   (Japan)

Author keywords

C C Bond Cleavage; Chiral N,O Acetal; Electrochemical Oxidation; Memory of Chilarity; Prolinol

Indexed keywords

EID: 67651083716     PISSN: 03855414     EISSN: None     Source Type: Journal    
DOI: 10.3987/COM-08-S(D)10     Document Type: Article

References (16)

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11. Methyl racemic-cis-3-methylprolinate was prepared by reported method, see. Lorthiois E., Marek I., and Normant J.F. J. Org. Chem. 63 (1998) 2442
12. Strong NOESY peaks illustrated in Figure 1 were observed between 3-methyl protons and the 2-methoxyl protons. No cross peaks were observed between the methoxyl protons and the proton at 3-carbon. On the basis of this result, the stereochemistry of the major diastereomer was deduced to be a cis configuration. {A figure is presented}Figure 1 NOESY for major oxidation product derived from 6
13. It can not be overruled that the repulsion of 3-methyl group and N-o-phenylbenzoyl group in iminium ion intermediate generated from 6 partially contributed the cis-methoxylation.
14. 10 the solvent was removed. The residue was subjected to silica gel chromatography to give 4 (37% yield, 50% ee) as a colorless oil and benzophenone (40 % yield). The optical purity of 4 was determined by HPLC analysis using Daicel Chiralcel OD (0.46 cmΨ × 25 cm). Condition: n-hexane : 2-propanol=9 : 1; wavelength, 254 nm; flow rate 1.0 mL/min; retention time, 6.6 min for (R)-4, 8.7 min for (S)-4.
15. Excess amount of electricity (2.5 or 3.0 F/mol) did not improve the yield and % ee of 4.
16. N-o-Phenylbenzoyl-α,α-diarylprolinol 5c-i were prepared by the Grignard reaction of N-o-phenyl-benzoyl-L-proline methyl ester with 2.2 equiv of the corresponding arylmagnesium bromide in THF (over 70% yields).