Bio-inspired synthesis of rare and unnatural carbohydrates and cyclitols through strain driven epimerization

Mohanrao, Raja; Asokan, Aromal; Sureshan, Kana M.

doi:10.1039/c4cc00868e

Cited by 7 publications

(5 citation statements)

References 40 publications

(9 reference statements)

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“…16 It is noteworthy that the Swern oxidation of 8 leads to epimerization of the transketal to cis-ketal 14; hence, it cannot be used for this transformation. 17 The reduction of enone 9 using K-selectride afforded alcohol 10 with the desired stereochemistry in 90% yield over two steps. The bulky hydride donor ensured hydride delivery from opposite side of the protected O-2.…”

Section: Resultsmentioning

confidence: 99%

Total syntheses and structural validation of lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K

Mondal

Sureshan

2014

Org. Biomol. Chem.

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Natural carbasugars are an important class of biologically active compounds. Due to their conformational freedom and the subtle difference in spectral characteristics between isomers, often their NMR-based structural assignments are erroneous. It is thus important to validate their structural identity through chemical synthesis. We report the first total syntheses and structural validation of five natural carbasugars, namely, lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K in their racemic forms, from a myo-inositol-derived common intermediate. This intermediate was synthesized by the vinylogous ring opening of myo-inositol orthoester cage under mild acidic conditions in six steps from myo-inositol. From this intermediate, we achieved the syntheses of (±)-lincitol A in six steps, (±)-lincitol B in seven steps, (±)-uvacalol I in five steps, (±)-uvacalol J in five steps, and (±)-uvacalol K in seven steps. The structure and relative stereochemistry of these natural products were confirmed by comparing the (1)H and (13)C NMR spectra of synthesised natural products with the reported data. These syntheses involved several unprecedented protecting-group manipulations and unexpected reactivities.

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Section: Resultsmentioning

confidence: 99%

Total syntheses and structural validation of lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K

Mondal

Sureshan

2014

Org. Biomol. Chem.

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“…[14] Nitrocyclitols belong to the large family of cyclitols (also found as carbocyclic polyols or carbasugars). [15][16][17][18] They are essentially found as synthetic precursors of aminocyclitols. [19,20] However natural nitrosugars moieties do exist and are derived from aminosugars via an oxidation step.…”

Section: Introductionmentioning

confidence: 99%

“…[17,23,24] Consequently, there have been continuous efforts in the last decade to prepare natural cyclitols and aminocyclitols as well as analogues with enhanced or more selective biological profiles in order to study in depth the influence of this moiety on their specific receptors. [15][16][17][18][25][26][27] Few years ago, we have reported that nitrocyclitols can be efficiently prepared by a one-pot multi-step chemoenzymatic synthesis, consisting of an aldol reaction catalyzed by an aldolase and an intramolecular spontaneous Henry reaction as key steps (scheme 1). On the one hand, starting from several nitrobutanals fructose-1,6-bisphosphate aldolase (FBA) [28][29][30] and fructose-6-phosphate aldolase (FSA) [20,31] have led to nitroaldols with 3S,4R (becoming 2S,3R in the final cyclitol) defined configurations.…”

Section: Introductionmentioning

confidence: 99%

l-Rhamnulose-1-phosphate and l-fuculose-1-phosphate aldolase mediated multi-enzyme cascade systems for nitrocyclitol synthesis

Bres¹,

Guérard-Hélaine²,

Hélaine³

et al. 2015

Journal of Molecular Catalysis B: Enzymatic

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One-pot multistep stereoselective cascade reactions were implemented for the straightforward synthesis of various nitrocyclitols. Two kinases, an aldolase and a phosphatase were involved in this process together with a spontaneous intramolecular Henry reaction to provide a nitrocyclitol moiety. The C-C bond formation catalyzed by the aldolase and the nitroaldol reaction were key steps to build the carbocycle stereoselectively. The acceptor substrates for aldolases were all 4-nitrobutanal structurally based, hydroxylated or not on C2 and/or C3 positions. On the one side, L-fuculose-1-phosphate aldolase (FucA) has catalyzed the formation of the expected (R,R; D-erythro) aldol except in the case of 4-nitrobutanal from which (R,S; L-threo) aldol was also present. On the other side, L-rhamnulose-1-phosphate aldolase has always provided the expected (R,S; L-threo) aldol together with minor amount of (R,R; D-erythro) aldol thus being less stereoselective than FucA. The intramolecular Henry reaction has occurred spontaneously on the aldol due to the presence of both ketone and terminally positioned nitro group. This cyclisation was stereoselective and correlated to the presence or not of a hydroxyl group in β to the nitro group. From 4-nitrobutanal as substrate and for one defined stereochemistry by the aldolase (R,R or R,S) one cyclitol was formed. In the other cases, two diastereomeric series were formed due to the presence of an R and S configured alcohol function in β to the nitro group. The combination of this set of reactions successfully furnished 11 nitrocyclitols never described before in literature.

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“…xylosides at C2, C3, and C4 by performing a Swern oxidation [319][320] or by oxidation with Dess-Martin periodinane 88,321 . Another method for epimerization is the transformation of the hydroxyl group into a better leaving group followed by an SN2 reaction.…”

Section: Modificationsmentioning

confidence: 99%

Chemistry of xylopyranosides

Thorsheim

Siegbahn

Johnsson

et al. 2015

Carbohydrate Research

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Xylose is one of the few monosaccharidic building blocks that are used by mammalian cells. In comparison with other monosaccharides, xylose is rather unusual and, so far, only found in two different mammalian structures, i.e. in the Notch receptor and as the linker between protein and glycosaminoglycan (GAG) chains in proteoglycans. Interestingly, simple soluble xylopyranosides can not only initiate the biosynthesis of soluble GAG chains but also function as inhibitors of important enzymes in the biosynthesis of proteoglycans. Furthermore, xylose is a major constituent of hemicellulosic xylans and thus one of the most abundant carbohydrates on Earth. Altogether, this has spurred a strong interest in xylose chemistry. The scope of this review is to describe synthesis of xylopyranosyl donors, as well as protective group chemistry, modifications, and conformational analysis of xylose.

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Bio-inspired synthesis of rare and unnatural carbohydrates and cyclitols through strain driven epimerization

Cited by 7 publications

References 40 publications

Total syntheses and structural validation of lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K

Total syntheses and structural validation of lincitol A, lincitol B, uvacalol I, uvacalol J, and uvacalol K

l-Rhamnulose-1-phosphate and l-fuculose-1-phosphate aldolase mediated multi-enzyme cascade systems for nitrocyclitol synthesis

Chemistry of xylopyranosides

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