The synthesis of 2,3-dideoxy-2-fluoro-3-C-methylpentose-containing nucleosides via [3,3]-sigmatropic rearrangements
摘要:
[3,3]-Sigmatropic rearrangement of in situ-formed [0,0]-silyl ketene acetals of butenyl fluoroacetates was used as the key step in the synthesis of racemic 2,3-dideoxy-2-fluoro-3-C-methylpentofuranoses. The product pentofuranoses were transformed further into pyrimidine and purine nucleosides. The conformations of the synthetic carbohydrates were confirmed by single-crystal X-ray diffraction studies and indicated that previous structural assignments made by NMR were in error.
Synthesis of α-fluoro β-substituted γ-unsaturated acid derivatives via a diastereoselective Claisenrearrangement of allyldifluorovinyl ethers is described.
Ester enolate Claisen rearrangements of allyl .alpha.-fluoroacetates and .alpha.-fluoropropanoates
作者:John T. Welch、Janet S. Plummer、Tso Sheng Chou
DOI:10.1021/jo00001a065
日期:1991.1
The ester enolate Claisen rearrangement of allyl alpha-fluoroacetates 1 forms 2-fluoroalkenoic acids 2 in good to excellent yield with good internal asymmetric induction. This selectivity was unexpected as stereoselective deprotonation of fluoroacetates is not normally possible. The selective formation of the required alpha-fluoro silyl ketene acetal 3 was found to result from the stereoselective rearrangement of the allyl alpha-fluoro-alpha-silylacetate isomer. Although silyl ketene acetals derived from alpha-fluoropropanoates 7 also rearranged, control of internal asymmetric induction was not possible.
WELCH, JOHN T.;PLUMMER, JANET S.;CHOU, TSO-SHENG, J. ORG. CHEM., 56,(1991) N, C. 353-359
作者:WELCH, JOHN T.、PLUMMER, JANET S.、CHOU, TSO-SHENG