A practical and scalable synthesis of carbohydrate based oxepines

Vannam, Raghu; Peczuh, Mark W.

doi:10.1039/c6ob00262e

Cited by 9 publications

(9 citation statements)

References 55 publications

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“…In our recent synthesis of oxepines, per‐ O ‐acetyl septanoses (i.e., 17 – 20 ) were the key intermediates. They were prepared by vinyl Grignard addition to benzyl‐protected pyranose lactols, followed by ozonolysis and protecting group manipulations . Once in hand, the per‐ O ‐acetates were converted into their anomeric bromides ( 21 , 22 ) and then the cyclic enol ether (oxepine) 23 via reductive elimination of bromide and acetate across the C1–C2 bond.…”

Section: Resultsmentioning

confidence: 99%

“…With these considerations in mind, acyl protected sugars, like per‐ O ‐acetyl septanoses 17 – 20 in Figure were chosen for the synthesis of the pNP septanosides. Inspiration for targeting per‐ O ‐acyl sugars as starting materials came from the known versatility of per‐ O ‐acetyl pyranoses in glycosylation reactions, as well as from our recent synthesis of acetate protected carbohydrate based oxepines where per‐ O ‐acetyl septanoses were key intermediates . Here we report the conversion of the glucose‐derived per‐ O ‐acetyl septanoses to anomeric halides and their subsequent glycosylations, including formation of the pNP septanosides.…”

Section: Introductionmentioning

confidence: 96%

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Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

et al. 2018

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Protein–carbohydrate interactions are at the heart of many biological processes. For lectins, those interactions result simply in the association of two species, whereas for enzymes like glycosidases, association ultimately leads to cleavage and formation of covalent bonds. We have investigated lectin–septanose interactions in the past. Here we report on a route to synthesize p‐nitrophenyl septanosides via the corresponding septanosyl halides. During the investigation we observed differential rates of glycosyl halide formation of the per‐O‐acetyl septanoses based on the stereochemistry at C1 and C2. Further, we observed unexpected stereoselectivities in glycoside bond formation that depended on a number of factors including the electrophilic sugar species, the incoming nucleophile, and reaction conditions. The results provided new parameters to consider when approaching septanose glycosylations. Even more importantly, the synthesis of p‐nitrophenyl septanosides will enable them to be used to interrogate septanose‐glycosidase binding and hydrolysis.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

et al. 2018

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“…The RCM route benefitted from its short lengththree stepsbut suffered from variable yields in the olefination step and limited throughput due to the high loading (25 mol %) and associated cost of the Schrock catalyst (>$1000/g). An alternative route was developed, therefore, that addressed the throughput challenge in particular . This second approach began with tetra- O -benzyl mannose 8 , which was subjected to a Grignard addition using vinyl magnesium bromide in the first step.…”

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confidence: 99%

“…The advantage of starting with 2,3;4,6-di- O -acetonide mannose 5 was that it would remove the hydrogenolysis and acetonide formation steps that were in the original reductive elimination sequence. , A method for the preparation of lactol 5 directly from d -mannose via acetonization using 2-methoxy propene was reported by Gelas and Horton . According to them, the reaction was under kinetic control.…”

mentioning

confidence: 99%

“…An alternative route was developed, therefore, that addressed the throughput challenge in particular. 21 This second approach began with tetra-O-benzyl mannose 8, which was subjected to a Grignard addition using vinyl magnesium bromide in the first step. The low diastereoselectivity of the reaction was of little concern because the new stereogenic center would ultimately be removed in the elimination step.…”

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confidence: 99%

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Synthesis of a Diacetonide-Protected, Mannose-Based Oxepine: Configurational Control of Anomeric Acetate Activation

Pero

Peczuh

2022

J. Org. Chem.

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Carbohydrate-based oxepines are seven-membered-ring oxacycles containing an enol ether moiety. These compounds have been used as intermediates in the preparation of septanose carbohydrates by functionalization through their double bond. Reported here is a new synthesis of a carbohydrate based oxepine that uses 2,3;4,6-di-O-acetonide mannose as a key starting material. The oxepine is an important precursor used in the synthesis of septanose glycomimetics of mannopyranosides. The central feature of the synthesis is a two-step sequence that converts a septanose 1,2-di-O-acetate to the septanosyl bromide and onward to the oxepine via a reductive elimination.

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Household Ozone Disinfector as An Alternative Ozone Generator for Ozonolysis of Alkenes

et al. 2021

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Ozonolysis is an oxidative cleavage reaction of alkenes with ozone that is indispensable and has found many applications in organic synthesis. However, dedicated laboratory ozone generators are quite expensive equipment and may not be affordable by many laboratories. Recently, lowcost ozone disinfectors have become more common as a household appliance. Herein, we demonstrate the applicability of a household ozone disinfector, which can produce ozone in the order of 10 mmol/h, as alternative equipment for the laboratory scale ozonolysis of alkenes. The ozonolysis of 14 styrene derivatives bearing electron-donating and electron-withdrawing groups on aromatic rings including those with αand β-substituents, as well as 8 natural products containing olefinic moieties were investigated. Ozonolysis of these alkenes at millimole scales proceeded to completion within 30-40 minutes and the carbonyl products were obtained in 68% to quantitative yields. Preparative-scale ozonolysis of 4-methoxystyrene (6.17 g, 46 mmol) was also demonstrated. The reaction proceeded smoothly to yield 4anisaldehyde in 92% yield, which was subsequently converted to p-anisaldehyde dimethyl acetal in 66% yield. This work presents household ozone disinfector as an affordable, compact size, and practical synthetic equipment that does not require extra modification. Thus, the household ozone disinfector offers convenient access to ozonolysis or other reactions involving ozone for low-budget laboratories.

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A practical and scalable synthesis of carbohydrate based oxepines

Cited by 9 publications

References 55 publications

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

Formation of and Glycosylation with Per‐O‐Acetyl Septanosyl Halides: Rationalizing Complex Reactivity En Route to p‐Nitrophenyl Septanosides

Synthesis of a Diacetonide-Protected, Mannose-Based Oxepine: Configurational Control of Anomeric Acetate Activation

Household Ozone Disinfector as An Alternative Ozone Generator for Ozonolysis of Alkenes

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