Electrostatic Effects on the Reactions of Cyclohexanone Oxocarbenium Ions
作者:Glen Baghdasarian、K. A. Woerpel
DOI:10.1021/jo060968z
日期:2006.9.1
Nucleophilic substitution reactions of 4-substituted cyclohexanone acetals display different selectivities depending upon the electronic nature of the substituent. Alkyl groups favor equatorial positions in the oxocarbeniumions, but alkoxy groups prefer axial conformers. The reactions of acetals with alkoxy groups constrained to either equatorial or axial positions suggest that the presence of an
2-Substituted 3-(trimethylsilyl)-1-propenes react with N-Boc-alpha-amino aldehydes in the presence of BF3.OEt(2) to give homoallylic alcohols, potential intermediates for the synthesis of hydroxyethylene peptide isosteres. The reaction gives a predominance of the syn products, but 2-(chloromethyl)-3-(trimethylsilyl)-1-propene (5) exhibits a higher stereoselectivity with respect to other analogous allylsilanes. We hypothesize that this selectivity is due to an ''ene'' reaction followed by desilylation in the reaction medium (BF3.OEt(2), CHCl3). This reaction shows applicability to the synthesis of potential HIV-1 protease inhibitors. The preparation of compound 3, which has a structure related to the potent inhibitor L-682,679, is described.
DAniello Fabiana, Mann Andre, Mattii Duccio, Taddei Maurizio, J. Org. Chem, 59 (1994) N 14, S 3762- 3768
作者:DAniello Fabiana, Mann Andre, Mattii Duccio, Taddei Maurizio
DOI:——
日期:——
Dipeptide isosteres. 2. Synthesis of hydroxyethylene dipeptide isostere diastereomers from a common γ-lactone intermediate. Preparation of renin and HIV-1 protease inhibitor transition state mimics.
作者:William R. Baker、John K. Pratt
DOI:10.1016/s0040-4020(01)81896-2
日期:1993.1
A general strategy for the synthesis of the hydroxyethylene dipeptideisostere diastereomers C or D has been developed. The syntheses proceeded through a common γ-lactone intermediate A or B. The C(3α) γ-lactone diastereomer A was prepared from the N-Cbz protected α-amino aldehyde and 2-(2-isopropylpropen-2-yl)trimethylsilane in five steps. The C(3β) γ-lactone diastereomer B was obtained by kinetic