exo-Glycal approaches to C-linked glycosyl amino acid synthesis

Campbell, Andrew D.; Paterson, Duncan E.; Taylor, Richard J. K.; Raynham, Tony

doi:10.1039/a905014k

Cited by 56 publications

(29 citation statements)

References 13 publications

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“…Scheme 12 presents a more elaborate method utilized to synthesize C-disaccharide 61, involving the sequential hydroboration of glycal 60 and triflate mediated Suzuki coupling [59]. Similar strategies were also reported by others [60][61][62]. Furthermore, our group reported a facile synthesis of spiro-sugars (Scheme 13) by hydroboration of exo-glycosyl dienes 62-64 [18,63], which favorably gave the α-isomers following an acidic workup.…”

Section: Application For C-glycoside Synthesissupporting

confidence: 52%

exo-Glycal Chemistry: General Aspects and Synthetic Applications for Biochemical Use

Lin¹,

Lin²,

Yang

2005

CTMC

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It is well known that carbohydrates play an indispensable role in a variety of essential biological activities, such as cell-cell adhesion, bacteria and virus infections, and tumor metastasis. Among an increasing number of sugars and sugar mimetics that have been designed and synthesized for the purpose of drug discovery, C-glycosides are considered to be one of the best choices on account of their stability and resemblance as they differ from normal glycosides only in glycosidic linkages. exo-Glycals are unsaturated sugars that have a double bond attached to the anomeric center outside the sugar ring. These carbohydrate molecules are useful for the synthesis of C-glycosides and compounds containing quaternary carbons, provided that the olefin can be properly reduced or functionalized. This review places special emphasis on two aspects of exo-glycals including general methods of preparation and synthetic applications for making biologically important molecules. The first half discusses the methods of addition/elimination and Ramburg-Bäcklund rearrangement that offer many beneficial features including a wide range of double bond substitutions, limited reaction steps, easy operation and good overall yields. The rest of the article demonstrates a number of synthetic studies using exo-glycals as the starting materials. The target molecules can be categorized into three groups, namely C-glycosides, enzyme inhibitors and bioactive natural products.

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Section: Application For C-glycoside Synthesissupporting

confidence: 52%

exo-Glycal Chemistry: General Aspects and Synthetic Applications for Biochemical Use

Lin¹,

Lin²,

Yang

2005

CTMC

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“…The stereoselective 9‐BBN hydroboration‐oxidation of 2a to give exclusively the β‐ C ‐glycoside 7 was initially described by RajanBabu and Reddy;3 Johnson and Johns have demonstrated that the intermediate organoborane can undergo palladium‐catalysed cross‐coupling reactions to give the aromatic C ‐glycoside derivatives 8 9. We have also recently reported the synthesis of a C ‐glycosyl amino acid by the Suzuki coupling of this organoborane with a vinyl iodide derived from the Garner aldehyde 10. In addition, we have carried out the dihydroxylation of exo ‐glycal 2a to produce the known tetrabenzyl‐α‐ D ‐ gluco ‐2‐heptulopyranose 9 {m.p.…”

Section: Resultsmentioning

confidence: 95%

A Ramberg−Bäcklund Approach to the Synthesis ofC-Glycosides,C-Linked Disaccharides, andC-Glycosyl Amino Acids

et al. 2002

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Synthetic applications of exo-glycals, derived from S-glycoside dioxides using the Meyers variant of the Ramberg−Bäcklund rearrangement, are described. These include a formal synthesis of a β-glycosidase inhibitor 12 and an efficient route to spirocyclic glucose derivatives 17 and [a] Scheme 2. exo-Glycals are versatile intermediates for the synthesis of more highly functionalised C-glycosides CHCl 3 )}. Sigmatropic rearrangements involving the enol ether function have recently been described: a Claisen rearrangement of 6-vinyl exo-glycals [12] and a ClaisenϪIreland rearrangement of 2-O-acyl exo-glycals [13] furnish cyclooctene and C-glycan derivatives, respectively. Exomethylenic sugars have also proved to be good substrates for ring-closing olefin metathesis: derivatives of 2a bearing an unsaturated side chain at position 2 have been shown to undergo ruthenium catalysed ring closure to give bicyclic glycosylidene compounds. [14] Postema and Calimente have also exploited this powerful carbonϪcarbon bond-forming process for the preparation of C1-substituted glycals [15a] and C-linked disaccharides. [15b] The phenyl-substituted exo-glycal derivative 2b is accessible in high yield and good stereoselectivity from the tandem halogenation-RambergϪBäcklund rearrangement of benzyl sulfone 1b (Scheme 1). We decided to explore the elaboration of this substrate (Scheme 3). When hydroboScheme 3. HydroborationϪoxidation of exo-glycal 2b to give the known C-glycoside 11Eur.

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“…This entailed a tandem boron‐mediated aldol addition [(−)‐Ipc 2 BCl, Et 3 N] and Sm‐promoted reduction (SmI 2 , EtCHO) sequence, proceeding via the alcohol intermediates 10 and 11 (53 %, 7 steps). The amine 12 was next coupled (EDC, HOBt) with 9 and the resulting amide cyclized to the oxazoline 3 (DAST, 73 %) . At this point, the lack of an electron‐withdrawing substituent on the oxazoline ring presented a potential problem, since the oxidation of unactivated oxazolines to the corresponding oxazoles can be challenging.…”

Section: Methodsmentioning

confidence: 99%

An Expedient Total Synthesis of Chivosazole F: an Actin‐Binding Antimitotic Macrolide from the Myxobacterium Sorangium Cellulosum

et al. 2016

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Au nified strategy for the chemical synthesis of the chivosazoles is described. This strategy is based on two closely related approaches involving the late-stage installation of the isomerization-prone (2Z,4E,6Z,8E)-tetraenoate motif,a nd an expedient fragment-assembly procedure.The result is ahighly convergent total synthesis of chivosazole Fthrough the orchestration of three mild Pd/Cu-mediated Stille cross-coupling reactions,i ncluding the use of ao ne-pot, site-selective,t hreecomponent process,incombination with controlled installation of the requisite alkene geometry.Thechivosazoles (Scheme 1) are astructurally unique family of bioactive polyene macrolides,w hich were first isolated by Hçfle and Reichenbach from the myxobacterium Sorangium cellulosum.[1] They show highly potent antiproliferative activity against cancer cell lines and have been proposed to function by inhibiting actin polymerization through specific binding to G-actin, thereby leading to disruption of cytoskeletal dynamics.While actin is increasingly being recognized as ap otential target protein in cancer chemotherapy, [2] the chivosazoles exhibit little structural homology with other known actin-binding ligands.[3] As ar esult, the exact binding site and mode of action of the chivosazoles are likely to be distinct, thus making them an intriguing chemotype for studying the actin cytoskeleton, as well as ap romising antimicrofilament lead candidate for drug discovery.From the perspective of molecular architecture,t he chivosazoles display an extraordinary array of features.T he signature 31-membered macrolactone ring features ten stereocenters,a no xazole moiety,a nd nine alkenes arranged in three distinct conjugated polyene arrays with diagnostic alternating E/Z geometry.[4] Thes ix known members of the family differ in the substitution in the 6-deoxyglucopyranoside appended at C11 and the C20 position, with chivosazole F(1)corresponding to the aglycon of chivosazole A(2). Despite,o rp ossibly because of,t heir complex and delicate nature,t here have been limited synthetic efforts reported toward the chivosazoles.N otably,t he first total synthesis of chivosazole Fw as achieved by Kalessesg roup, [5a,b] which served to validate their earlier configurational assignment. [4] Scheme 1. Retrosynthetic analysis of the chivosazoles, highlightingthe key fragments for site-selectiveStille cross-coupling reactions. The same bond disconnections are used in Approaches Iand II but their ordering in the forward synthetic sense is different. HWE = HornerWadsworth-Emmons, TBS = tert-butyldimethylsilyl, TES = triethylsilyl.

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exo-Glycal approaches to C-linked glycosyl amino acid synthesis

Cited by 56 publications

References 13 publications

exo-Glycal Chemistry: General Aspects and Synthetic Applications for Biochemical Use

exo-Glycal Chemistry: General Aspects and Synthetic Applications for Biochemical Use

A Ramberg−Bäcklund Approach to the Synthesis ofC-Glycosides,C-Linked Disaccharides, andC-Glycosyl Amino Acids

An Expedient Total Synthesis of Chivosazole F: an Actin‐Binding Antimitotic Macrolide from the Myxobacterium Sorangium Cellulosum

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