Synthesis of pyrrolidine homoazasugars and 3,4-dihydroxy-5-hydroxymethylprolines using aldol additions of metalated bislactim ethers to 2,4-O-ethylidene-d-erythroses
syn-stereoselectivity of the aldol addition to β-protected 2,4-O-ethylidene-erythroses. In the addition to the “unprotected” 2,4-O-ethylidene-erythrose, the preference for chair-shaped transition structures in which the erythrose moiety is involved in a six-membered chelate ring is consistent with the experimentally observed syn,anti-stereochemical outcome. The preparative utility of the aldol-based approach was demonstrated
Trifluoromethylation of sugar 1,4-lactones : Synthesis of 5-deoxy-5,5,5-trifluoro-D and L-ribose and lyxose derivatives
作者:Pascal Munier、Dominique Picq、Daniel Anker
DOI:10.1016/s0040-4039(00)61400-4
日期:1993.12
The four 5-deoxy-5,5,5-trifluoro-D and L-ribo and -lyxo furanoses were synthesized from lactones using CF(3)SiMe(3) in 5 or 6 steps and 30-40 % overall yield. The key step was a stereoselective reduction of 1,1,1-trifluoror-2-ketoses with LialH(4) or NaBH4 at an anomeric centre.
Stéréosélectivité comparée de la réduction de trifluorométhylcétones et des méthylcétones correspondantes: nouvelles voies d'accès à des dérivés trifluorométhylés de pentoses
corresponding methylketones; the results -in accordance with literature- show an important steric hindrance of the CF3 group. The selectivity observed in these reductions led to good yields in the syntheses of 5,5,5-trifluorinated derivatives of D and L-pentofuranoses; a new method for the preparation of some functionalized trifluoromethylketones is described.