Regioselective Ring Opening of 1,3‐Dioxane‐Type Acetals in Carbohydrates

Abstract

The (regio)selective manipulation of hydroxyl groups in carbohydrates has been a long‐standing challenge in (bio)organic chemistry and continues to trigger the creative minds of many chemists. Among the various strategies that have been developed to address these issues, mostly relying on multistep procedures involving the use of protecting groups, the regioselective ring opening of 1,3‐dioxane‐type acetals has emerged as a powerful tool. Since the first papers on this subject appeared in the 1960s, a large variety in both acetal types and reagents for their partial cleavage has come to the fore. This review aims to give an overview of the different carbohydrate‐derived ring systems, ranging from four‐ to seven‐membered rings, on which regioselective ring‐openings have been performed, along with the appropriate reagents and combinations thereof. The transformations on 1,3‐dioxane acetals fit in a larger group of ring opening reactions of structurally related cyclic functional groups, including 1,3‐dioxolanes, 1,3‐oxathianes, orthoesters, cyclic carbonates and silylene acetals, which will not be discussed in this review.

Stereochemistry of Simple Molecules inside Nanotubes and Fullerenes: Unusual Behavior of Usual Systems

“…It is known that 1,3-dioxanes-very attractive heteroanalogs of cyclohexane-belong to the classical objects of conformational analysis [94]. Besides that, due to their wide range of pharmacological action, they may be used for the creation of new drugs [205,206] and also as reagents in fine organic synthesis [207][208][209][210][211]. All this makes it relevant to consider the conformational properties of these compounds inside nanotubes, from the perspectives of nanoreactors [68][69][70][71][72][73][74][75] and drug delivery systems [15,19].…”

Regioselectivity of Cobalamin‐Dependent Methyltransferase Can Be Tuned by Reaction Conditions and Substrate

“…Finally, the resin was removed by filtration, and the resulting solution was evaporated under reduced pressure to the crude product which was purified via column chromatography cyclohexane/EtOAc (8 : 2 v/v) to afford 1 f (201 mg, 1.3 mmol, yield 78 %). Spectroscopic data were superimposable with those of the pure standard of 1 f. 1…”

“…Controlling regioselectivity in a chemical transformation represents a challenge, since the differentiation between identical chemical groups within a single molecule can in general only be addressed by exploiting steric effects. Thus, the regioselectivity observed may be a result either of the specific properties of the substrate, [1] or in a more general approach be controlled by the reagent or the catalyst. Consequently, beside metalorganic catalysts [2] mainly biocatalysts [3] have been reported for regioselective transformations like for instance in hydrolytic reactions, [4] CÀ H oxidation, [5] amination, [6] Baeyer Villiger oxidation, [7] and nitration, [8] just to mention a few.…”

Synthesis of carbohydrate building blocksviaregioselective uniform protection/deprotection strategies

“…Many methods have been developed to dedicated to this topic, 121 and a very recent review by Janssens et al offers the most up to date coverage of the topic. 122 Discussed herein are only some representative examples relevant to the topic of this review. In 1969, Bhattacharjee and Gorin applied the mixed hydrides in the reduction of carbohydrate series for the first time.…”

“…Other useful methods to affect the regioselective opening of benzylidene include DIBAL, 135–138 Et 3 SiH-TFA, 139 Et 3 SiH-BF 3 ·Et 2 O, 140 BH 3 •THF-Bu 2 BOTf, 141 BH 3 •NMe 3 -Me 2 BBr at −78 °C, 142 BH 3 in combination with metal triflates at rt, 143 BH 3 or Me 2 EtSiH with Cu(OTf) 2 , 144 BH 3 •THF and CoCl 2 , 145 Et 3 SiH and I 2 , 146 among others. 122 The development of new methods has been complemented by a variety of mechanistic investigations. 147–152 4-Methoxybenzylidene acetals can also be selectively opened in a similar fashion and using similar reagents to as benzylidene acetals.…”