With -threitol

The initial investigation focused on the use of threitol-derived auxiliaries with various substituent groups on the dioxolane ring (Table 3.3). However, it became evident that the oxygen atoms in the substituents had a detrimental effect on selectivity. Comparison of the diastereoselectivities for the ketals 69-71, which contain Lewis basic sites in the substituents at the 1 and 2 positions, with those from simpler diol derived ketals 72-74 demonstrates the conflicting effects of numerous coordination sites. The simpler, diol-derived ketals provide superior results compared to the threitol derived ketals. The highest diastereoselectivity is observed in the case of the 1,2-diphenyl ethane-1,2-diol derived ketal 74. 

Products were analyzed via Waters Model 515 HPLC Pump fitted with a Waters model 2410 refractive index detector. Separations was performed via an Aminex HP-87H 300mm column at 65°C using 0.005M H2SO4 as the mobile phase. Compounds calibrated for this work included xylitol, arabitol, erythritol, threitol, PG, EG, glycerol, lactate, 1-propanol, 2-propanol, ethanol, methanol, and the butanetriol isomers. Any compounds not visible by RID were not quantified in this work. 

Fig. 19. A series of 2nd-generation dendrimers with chiral spacers derived from (R,R)- or (S,S)-tartaric acid. Note that the (R,R)-threitol-acetonide building blocks in 49 - 51 are derived from (S,S)-tartaric acid, and vice versa [78-80]...

Among the 1,4-di-O-substituted-L-threitol derivatives (Figure 14a) the one that has found most use in chiral crown ether synthesis is the 1,4-dibenzyl ether. Not only has it provided (88, 106, 107) a ready entry into the chiral tetrasub-stituted 18-crown-6 derivatives ll-31 to ll-34, but it has also proved to be a usehil chiral precursor for the preparation of chiral disubstituted 9-crown-3 (107), 12-crown-4 (108), 15-crown-5 (108), and 18-crown-6 (109) derivatives l-57, l-58, l-59, and l-60, respectively. In the preparation of l-S8 the base-promoted cyclization with triethylene glycol ditosylate is best carried out (108) with a... 

B. 2,3-Di-0 iaopropylidene-L-threitol (Note 13). In a dry, 2-L, threenecked, round-bottomed flask equipped with a 500-mL pressure-equalized addition funnel, reflux condenser, thermometer, and a large magnetic stirring bar. Is suspended lithium aluminum hydride (36 g, 0.95 mol) (Note 14) In diethyl ether (600 mL) (Note 15) under argon. The mixture Is stirred and heated to reflux for 30 min. Heating is discontinued while a solution of... 

D. 1,4-Di-O-benzyl-L-threitol. The crude ketal is dissolved in methanol (300 mL), 0.5 N hydrochloric acid (30 idL) is added, and the resulting mixture Is heated to reflux. Acetone and methanol are slowly distilled off (Note 29). Additional methanol (50 mL) and 0.5 N hydrochloric acid (20 mL) are added and the mixture Is kept at room temperature until ketal hydrolysis Is complete. The mixture Is diluted with saturated sodium bicarbonate solution (500 mL) and extracted with ether (3 x 500 mL). The ether extracts are combined, dried over anhydrous magnesium sulfate, and filtered. Removal of volatile material under reduced pressure gives crude l,4-di-0-benzy1-L-threitol as a pale yellow solid. This solid is recrystallized twice from chloroform/hexanes, to provide 59-65 g (195-215 mmol, 57-63% yield) of pure diol, up 54-55 C (Notes 30 and 31). Concentration of the mother liquors from the recrystallizations gives a yellow solid which is chromatographed on 70-230 mesh silica gel 60 (500 g) (Note 32), and eluted with 50% ethyl... 

Figure 11. The uptake of O3 by a. sulfhydryl reagent. A. Semilogarithmic kinetic plot of O3 uptake by Dithio-threitol (DTT). The ozone uptake was calculated as described in Figure 8. Numbers at the side of the graph refer to final concentrations of added DTT. Different symbols represent different experiments. B. Log-dog plot of rate constant and total O3 taken up with DTT concentrations. The rate constant (K) of O3 uptake and total (O3) were calculated from Part A.

Galbis and Munoz-Guerra et al. used the secondary G-protected L-threitol, L-arabinitol and xylitol (5-12) as monomers for the preparation of a series of linear [/M, ]-type polyurethanes 97 and 98 by polycondensation in solution with... 

Hartman and R. Barker synthesized 1,4-anhydroerythritol (3) by the saponification of 1-O-p-tolylsulfonyl-D-erythritol (1). The reaction apparently proceeded by direct reaction of the 4-hydroxyl group with the 1-p-tolylsulfonoxy group, and not through the intermediate formation of the 1,2-anhydride, which would have afforded the epimer, namely, 1,4-anhydro-D-threitol (2). Similarly, 1-O-p-tolylsulfonyl-D-threitol gave 1,4-anhydro-D-threitol (2). 

Bromohydrins 161 and 162 were converted57 into peracetylated erythritol and DL-threitol on treatment with potassium acetate in anhydrous acetic acid. 

Esterification of 622, and reaction of the ester with acetone furnished 623, which was reduced to 4-deoxy-2,3-0-isopropylidene-D-threitol (624). This substrate was further employed332 for the synthesis... 

For quality control, 100 pi pooled urine spiked with 8 pmol/1 sedoheptitol and 8 pmol/1 perseitol is included in each series. In addition, a 4 x dilution of this sample and a pooled urine spiked with 180 pmol/1 erythritol, 90 pmol/1 threitol, 218 pmol/1 arabitol, 36 pmol/1 xylitol, 18 pmol/1 ribitol, 36 pmol/1 sorbitol, 145 pmol/1 mannitol, 55 pmol/1 galactitol, 16 pmol/1 sedoheptitol and 16 pmol/1 perseitol are included in each series. These three urine samples were chosen to obtain concentrations in the low, middle and high part of the calibration curves. 

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