Glycerol acetonide

Several enzymatic procedures have been developed for the synthesis of carbohydrates from acyclic precursors. Aldolases appear to be useful catalysts for the construction of sugars through asymmeteric C-C bond formation. 2-deoxy-KDO, 2-deoxy-2-fluoro-KDO, 9-0-acetyl sialic acid and several unusual sugars were prepared by a combined chemical and enzymatic approach. Alcohol dehydrogenases and lipases have been used in the preparation of chiral furans, hydroxyaldehydes, and glycerol acetonide which are useful as building blocks in carbohydrate synthesis. 

Irreversible Transesterification. A new preparation of chiral glycerol acetonide (2,2-dimethyl-l,3-dioxolane-4-methanol) involving an enantioselective hydrolysis of 2-0-benzylycerol diacetate to the (R)-monoacetate catalyzed by a lipoprotein lipase (47) has recently been developed. In an effort to prepare the (S)-enantiomer, we have used the aforementioned irreversible transesterification reaction using isopropenyl acetate as an acylating reagent, which upon reaction gives acetone as a... 

The problem with enzyme catalyzed reversible transesterifications as an approach to biochemical resolution is that due to the reversible nature of the reaction, the enantiomeric excess of the desired product in the forward reaction decreases as the reverse reaction proceeds. As in hydrolytic reactions, the irreversible transesterification offers a better process for optimization of the transformation and for recovery of the product. Furthermore, there is no product inhibition observed in the irreversible process. Both enantiomers can be converted to glycerol acetonide with known procedures. 

Figure 10. Preparation of chiral glycerol derivatives and D- and L-glycerol acetonide. a 1. Hj/Pd-C 2. methyl isopropenyl ether/pyridinium p-toluensulfonate 3. K2C03/Me0H...

Figure 12. NMR determination of the enantiomeric excess of glycerol acetonide without separation of the unreacted ester. Approximately 1.35 mmol of a mixture of glycerol acetonide and the acetate ester was dissolved in a 10 mm NMR tube. To the solution was added 0.45 mmol of PCI,. The tube was shaken and quickly uncapped to allow the escape of the HCl gas formed during the reaction. After the recapped tube stood for 30 min at room temp, 0.5 mL of CDCI3 was added, and the NMR spectrum was recorded on a Varian 200 MHz instrument. The ee was calculated from Korean s formula (ee = (K - 1)/(K + 1), Vigneron, J.P. Dhaenens, M. Horeau, A. Tetrahedron. 1973,...

Yang and co-workers introduced chirality in their opening sequence by reacting (5)-glycerol acetonide (87) with 2,3,4-trifluoro, 1-nitrobenzene (45) to yield ether 88 (Scheme 4.14) (Yang et al., 1999). Deprotection of the acetonide under standard conditions delivered diol 89, which was treated with hydrogen bromide in acetic acid to give a mixture... 

M. E. Jung and T. Shaw, Total synthesis of (R)-glycerol acetonide and the antiepileptic and hypotensive drug (-)-y-amino-/l-hydroxybutyric acid (GABOB) use of vitamin C as a chiral starting material, J. Am. Chem. Soc., 102 (1980) 6304-6313. 

Coupling of the acid (81) with (jR)-glycerol acetonide (82), followed by formation of cyclic phosphate by reacting with... 

G. Hirth, W. Walther, Synthesis of the (R)-and (S)-glycerol acetonides. Determination of the optical purity, Helv. Chim. Acta 1985, 68, 1863. 

Isopropylidene-D-erythrose has been obtained from 0-arabinose by a route which does not involve the intermediacy of the lactone.All of these processes suffer from either relatively low overall yields or the requirement of a large number of individual stages. The procedure described here, which is based on a similar oxidative degradation of L-ascorbic acid (vitamin C) to L-threonic acid, is undoubtedly the most expeditious route to the acetonide of Q-erythronolactone available. In addition, the starting material, erythorbic acid, is an inexpensive and readily available substance, commonly used as a food preservative. It is pertinent to note that recently L-ascorbic acid has itself found synthetic utility as a precursor to (R)-glycerol acetonide, an Important C3 chiral synthon, ... 

A convenient preparation of L-(S)-glyceraldehyde acetonide from L-ascorbio acid en route to glycerol acetonide is described more fully in Chapter 24 An alternative method to that of Dondoni ot al. 

Optically active epihalohydrins were synthesized starting from (S)-glycerol acetonide which was obtained from D-mannitol. 

The synthetic scheme of (S)- and (R)-epichlorohydrins from (s)-glycerol acetonide via tosylation and chlorination was reported by McClure.16 We explored the general synthetic scheme to (R)-epihalohydrins. 

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