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1998 Fiscal Year Final Research Report Summary

ASYMMETRIC SYNTHESIS OF TERTIARY ALLYLIC ALCOHOLS AND EPOXIDES USING TETRASUBSTITUTED PYRROLIDINE AUXILIARIES.

Research Project

Project/Area Number 09650950
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Synthetic chemistry
Research InstitutionYOKOHAMA NATIONAL UNIVERSITY

Principal Investigator

HONDA Kiyoshi  FACULTY OF ENGINEERING,ASSOCIATE PROFESSOR, 工学部, 助教授 (60231578)

Project Period (FY) 1997 – 1998
KeywordsALLYLAMINE N-OXIDE / [2,3] SIGMATROPIC REARRANGEMENT / ASYMMETRIC INDUCTION / DIASTEREOFACIAL SELECTIVE REACTION / OPTICALLY ACTIVE TERTIARY ALCOHOL / OPTICALLY ACTIVE INALOOL / C_2-SYMMETRIC PYRROLIDINE / ASYMMETRIC EPOXIDE
Research Abstract

Geranylamines were prepared from geranyl bromide and various chiral pyrrolidine derivertives. Oxidation of the geranylamines with 1.1 equivalent of peracetic acid in dichioromethane at -60゚C led to labile allylamine N-oxides, which were, without isolation, rearranged to the trisubstituted hydroxyamines. Asymmetric inductions were dependent upon the rearrangement temperature and substituents R^1 and R^2, On the point of rearrangement temperature, lower temperature increased diastereomeric excess (de) of the hydroxyamines. For example, C_2-symmetrical pyrrolidine (R^1 = EtO, R^2 = EtOCH_2) gave 35%, 50% and 60% de at 80゚C, 25゚C and -30゚C, respectively. Furthermore, sterically more hindered C_2-symmetrical pyrrolidine (R^1 = MeO, EtO ; R^2 = TBSOCH_2) gave good result (de =65 - 70%) and fairly good results (de =60-65%) were obtained when using C_2-symmetrical pyrrolidine (R^1=MeO, EtO ; R^2 = MeOCH_2, EtOCH_2, Me). Finally, the tertiary allylic alcohol (R)-linalool was obtained without racemization by ultrasound-assisted reductive cleavage of N-O bond with zinc in acetic acid at 55゚C.The pyrrolidine auxiliary was separated during the work-up procedure and recycled. The absolute configuration and enantiomeric excess were determined by gas chromatography of synthetic linalool on a chiral stationary phase. The oxidation followed by rearrangement of nerylamine under similar conditions led to the inverse configuration (S) of the new stereogenic center as expected.
In summary, the asymmetric [2,3]sigmatropic rearrangement using a new C_2-symmetrical pyrrolidine auxiliary is described. Subsequent reductive cleavage of N-O bond provides (R)-linabool (licareol) from geranylpyrrolidine. Similary, (S)-linalool (coriandrol) is obtained from nerylpyrrolidine.

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Published: 1999-12-08  

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