Cycloadducts from highly functionalized nitrones and oximes as ligands in the enantioselective addition of diethylzinc to benzaldehyde

Synthesis of Optically Active 1,4-Dioxane Nucleotide Analogs

“…[9] The optical activity was introduced through the application of L-tartaric acid, which is an inexpensive and readily available chiral pool starting material. Construction of the dioxane moiety was first prepared the monoallylether of (2R,3R)-dimethyl tartrate by the reaction of dimethyl tartrate with allyl bromide in the presence of silver oxide, [10] yielding product 1, usually in good yields, (Scheme 1). This transformation was, however, difficult to reproduce, as yields depended on the quality of the silver oxide reagent.…”

Synthesis of a Novel, Optically Active Uridine Analog Containing a 1,4-Dioxane Sugar Moiety. Synthesis of the Corresponding Dinucleotide

“…Initially (2R,3R)-dimethyl tartrate was converted into the corresponding enantiomerically pure allyl ether 3 either by the reaction with allyl bromide in the presence of silver oxide [4] or in a tin assisted reaction with dibutyltin oxide. [5] Allylether 3 was next reduced to triol 4, either using LiAlH 4 [6] in 26% isolated yield, or as a viable alternative by reduction with NaBH 4 [7] which gave 4 in 88% yield.…”

“…This product was obtained by reduction of 3 with either LiAlH 4 or NaBH 4 . LiAlH 4 reduction: To a suspension of LiAlH 4 (3.72 g, 95%, 93 mmol) in dry diethyl ether (50 mL) was drop wise added a solution of 3 (4.36 g, 20 mmol) in 4 mL of diethyl ether at 0-5 • C. The reaction mixture was refluxed for 18 hours and then cooled in an ice bath.…”

“…This compound was prepared from dimethyl l-tartrate, 2, as described earlier [14] either by reaction with allyl bromide and silver oxide, 4 resulting in variable yields between 20 and 84% or by a reaction involving dibutyltin oxide 5 resulting in a 70% overall yield. B.p.…”

Synthesis of a Novel Benzoyl Adenosine Analog Containing a 1, 4-Dioxane Sugar Analog and the Synthesis of a Corresponding Uracil Adenine Dinucleotide

“…The tartrate was first converted into the corresponding enantiomerically pure diethyl ( 2R , 3R )-2- O -allyltartrate either by the reaction with allyl bromide in the presence of silver oxide or in a tin assisted reaction with dibutyltin oxide [9,10,11]. The allyl ether was reduced by LiAlH 4 [12,13,14] or NaBH 4 [15,16] to give a triol which was protected as an acetal with 2,2-dimethoxy-propane in the presence of p- toluene sulfonic acid.…”