Selective oxidation of glycosyl sulfides to sulfoxides using magnesium monoperoxyphthalate and microwave irradiation

Efficient Strategy for Characterization and Quantification of Polyunsaturated Lipids by Microwave-Assisted MMPP Epoxidation

Lipids play integral roles in biological processes, with carbon-carbon double bonds (C═C) markedly influencing their structure and function. Precise characterization and quantification of unsaturated lipids are crucial for understanding lipid physiology and discovering disease biomarkers. However, using mass spectrometry for these purposes presents significant challenges. In this study, we developed a microwave-assisted magnesium monoperoxyphthalate hexahydrate (MMPP) epoxidation reaction, coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS), to analyze unsaturated lipids. Microwave irradiation expedited the MMPP epoxidation, achieving complete derivatization in 10 min without byproducts. A diagnostic ion pair, displaying a 16 Da mass difference, effectively identified the location of the C═C bond in mass spectra. Microwave irradiation also significantly facilitated the epoxidation reaction of polyunsaturated lipids, achieving yields greater than 85% and yielding a complete epoxidation product. This simplifies chromatographic separation and aids in accurate quantification. Additionally, a purification process was implemented to remove excess derivatization reagents, significantly reducing mass spectrometry response suppression and enhancing analytical reproducibility. The method's effectiveness was validated by analyzing unsaturated lipids in rat plasma from a type I diabetes model. We quantified nine unsaturated lipids and characterized 42 fatty acids and glycerophospholipids. The results indicated that unsaturated fatty acids increased in diabetic plasma while unsaturated glycerophospholipids decreased. Furthermore, the relative abundances of Δ9/Δ11 isomer pairs also exhibited a close association with diabetes. In conclusion, microwave-assisted MMPP epoxidation coupled with LC-MS/MS provides an effective strategy for characterization and quantification of polyunsaturated lipids, offering deeper insight into the physiological impact of unsaturated lipids in related diseases.

Utilizing Reusable Catalyst Phosphotungstic Acid for the Synthesis of Thioglycoside from Per-O-acetyl Saccharides with Microwave-Assisted and De-O-acetylation with Methanol

Traditional methods for synthesizing complex oligosaccharides currently developed are not efficient, requiring a new glycosylation methodology. Herein, using phosphotungstic acid (PTA) as a catalyst has demonstrated to be a simple possibility for carbohydrate synthesis. The methodology is engineered into a PTA-catalyzed thioglycoside preparation under microwave conditions and de-O-acetylation of carbohydrates. These easier operations and convenient protocols display a wide substrate scope. Moreover, both methods can be developed into a one-pot reaction for the efficient synthesis of carbohydrate analogues.

Synthesis and Isolation of Diastereomeric Anomeric Sulfoxides from a d-Mannuronate Thioglycoside Building Block

Methyl [S-phenyl 4-O-acetyl-2,3-di-O-benzyl-1-thio-α-d-mannopyranoside (R/S)S-oxide] uronate was synthesised from a thioglycoside mannosyl uronate donor in a 98% yield. By using one equivalent of meta-chloroperbenzoic acid (m-CPBA) as the sulphur oxidant, a smooth conversion to the diastereomeric sulfoxide products was achieved. The product was fully characterized by 1H, 13C and 2D NMR alongside MS analysis.

Synthesis of glycosyl sulfoximines by a highly chemo- and stereoselective NH- and O-transfer to thioglycosides

The first highly stereoselective sulfoximine formation directly from sulfides is achieved in the preparation of unprecedented glycosyl sulfoximines. X-ray analysis and a computational model establish the configuration at sulfur.

Phenyliodine(III) Diacetate/I2 -Mediated Domino Approach for Pyrrolo[1,4]Thiazines and 1,4-Thiazines by a One-Pot Morin Rearrangement of N,S-Acetals

An efficient domino transformation using a phenyliodine(III) diacetate (PIDA)/I₂ combination towards Morin 1,4-thiazine compounds has been developed starting from N,S-acetals. The latter leads to "one-step" regioselective methylene insertion without the need for traditional sulfoxide intermediates in good yields. The reaction involves easily accessible N,S-acetals obtained from cost-effective basic ketones and cysteamine as starting materials. This process ultimately leads to 1,4-thiazines related to natural product and fused derivatives necessary for further QSAR study.

Magnesium bis(monoperoxyphthalate) hexahydrate as mild and efficient oxidant for the synthesis of selenones

A new, efficient and mild method for the direct oxidation of selenides to selenones using magnesium bis(monoperoxyphthalate) hexahydrate (MMPP) has been developed. Noteworthy this transformation proceeds at room temperature, employs a cheap and safety oxidant and has a broad functional group tolerance. Moreover, the produced selenones could be useful intermediates for the synthesis of different heterocyclic compounds.

Efficient oxidation of oleanolic acid derivatives using magnesium bis(monoperoxyphthalate) hexahydrate (MMPP): A convenient 2-step procedure towards 12-oxo-28-carboxylic acid derivatives

A new, straightforward and high yielding procedure to convert oleanolic acid derivatives into the corresponding δ-hydroxy-γ-lactones, by using the convenient oxidizing agent magnesium bis(monoperoxyphthalate) hexahydrate (MMPP) in refluxing acetonitrile, is reported. In addition, a two-step procedure for the preparation of oleanolic 12-oxo-28-carboxylic acid derivatives directly from Δ(12)-oleananes, without the need for an intermediary work-up, and keeping the same reaction solvent in both steps, is described as applied to the synthesis of 3,12-dioxoolean-28-oic acid.

Synthesis and use of sulfonamide-, sulfoxide-, or sulfone-containing aminoglycoside-CoA bisubstrates as mechanistic probes for aminoglycoside N-6'-acetyltransferase

Aminoglycoside-coenzyme A conjugates are challenging synthetic targets because of the wealth of functional groups and high polarity of the starting materials. We previously reported a one-pot synthesis of amide-linked aminoglycoside-CoA bisubstrates. These molecules are nanomolar inhibitors of aminoglycoside N-6'-acetyltransferase Ii (AAC(6')-Ii), an important enzyme involved in bacterial resistance to aminoglycoside antibiotics. We report here the synthesis and biological activity of five new aminoglycoside-CoA bisubstrates containing sulfonamide, sulfoxide, or sulfone groups. Interestingly, the sulfonamide-linked bisubstrate, which was expected to best mimic the tetrahedral intermediate, does not show improved inhibition when compared with amide-linked bisubstrates. On the other hand, most of the sulfone- and sulfoxide-containing bisubstrates prepared are nanomolar inhibitors of AAC(6')-Ii.

Recent trends in the synthesis of O-glycosides of 2-amino-2-deoxysugars

The discovery of new methods for stereoselective glycoside synthesis and convergent oligosaccharide assembly has been critical for the area of glycosciences. At the heart of this account is the discussion of the approaches for stereoselective synthesis of glycosides of 2-amino-2-deoxysugars that have emerged during the past two decades. The introductory part provides general background information and describes the key features and challenges for the synthesis of this class of compounds. Subsequently, major approaches to the synthesis of 2-amino-2-deoxyglycosides are categorized and discussed. Each subsection elaborates on the introduction (or protection) of the amino functionality, synthesis of glycosyl donors by introduction of a suitable leaving group, and glycosidation. Wherever applicable, the deprotection of a temporary amino group substituent and the conversion onto the natural acetamido functionality is described. The conclusions part evaluates the current standing in the field and provides a perspective for future developments.

An armed-disarmed approach for blocking aglycon transfer of thioglycosides

Thioglycosides are used frequently as glycosyl donors and as mimetics of O-glycosides. While being very useful, thioglycosides are prone to a detrimental side reaction referred to as aglycon transfer. In this paper, it is shown that aglycon transfer can be blocked by matching thioglycoside-containing acceptors with more armed glycosyl donors.