Structure and conformation of cis and trans-3,5-dimethylvalerolactones

Lanthanide shift reagents. Survey

“…Soc., 91, 5160 (1969). riety of functional organic molecules including alcohols,113-5'7-9•15'16•18 amines,3,1°•13,15,18 ketones, 3,11,14,18 aldehydes,318 sulfoxides,6•17 and esters; 12,13,16,18119 (2) the observation3 that Eu(dpm)8 is more efficient in effecting such shifts than is Eu(dpm)8(py)2, presumably owing to the lack of competition with pyridine for coordination sites; (3) the discovery4 that Pr(dpm)3 causes upfield shifts of larger magnitude than the downfield displacements induced by Eu(dpm)3 and the observa-tion13 of shifts for substrates in the presence of dpm complexes of Sm, Tb, Ho, and Yb as well; (4) the in-troduction10 of the chiral chelate, tris[(+)-3-pivaloylcamphorato]europium(III), a shift reagent for the determination of enantiomeric purity; (5) the observation that certain other lanthanide complexes4 as well as ß-diketonate chelates with less bulky substituents18,21 than Ln(dpm)3 are inefficient as shift reagents, very likely owing to the lack of a preferred orientation of the substrate molecule when the stereochemical rigidity and the bulky substituents of the chelate rings are absent; (6) the finding19 that partially fluorinated chelates of a similar variety are superior shift reagents because of propitious solubility and Lewis acidity characteristics.…”

Structure and conformation of N-benzoyl derivatives of the biologically important 3-amino-2,3,6-trideoxy-L-hexoses and their synthetic precursor γ- and δ-lactones; a1H and13C nuclear magnetic resonance study

“…' *CO,Et NHZ In view of the current interest in efficient total syntheses studying 4 9 5 non-carbohydrate-based chiral preparations of suitably protected forms of L-acosamine (17) and Ldaunosamine (18), and of the other two configurational isomers, L-ristosamine (20) and compound (19), belonging to the L -Y ~~o -and L-xyZo-series, respectively. Our synthetic strategy is based on the use of the NHR NHR optically active C , aldehydes (1)-(3) in constructing…”

“…afforded the required amino-sugar derivatives (17), (19), ~~c o 2 ~~ (18), and (20), respectively. Also the lactone (12), belonging to the D-SerieS, served as,precursor of Lacosamine (17) and, eventually, of L-daunosamine (18).…”

Lanthanide nmr shift reagents. A powerful new stereochemical tool

“…Applications of Eu(DPM)3 to structural and conformational studies are many and varied (9-11, 13, 15, [17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Classic examples are the first order spectra of n-hexanol and benzyl alcohol obtained by Sanders and Williams (15) using this shift reagent (see figure).…”