Reconsidering glycosylations at high temperature: precise microwave heating.

Area of Science:

• Organic Chemistry
• Carbohydrate Chemistry
• Synthetic Chemistry

Background:

• Traditional glycosylation methods often require strong Lewis acids and sub-ambient temperatures, limiting their efficiency and scope.
• Older literature suggests high-temperature glycosylations are feasible, particularly for phenols, but these methods are not widely adopted.
• The use of methyl 3,5-dinitrosalicylate (DISAL) as an anomeric leaving group offers a pathway for neutral glycosylation conditions.

Purpose of the Study:

• To develop a fast and efficient method for oligosaccharide synthesis using microwave heating.
• To investigate the applicability of neutral glycosylation conditions at high temperatures.
• To evaluate microwave heating as a general protocol for assessing novel glycosyl donors.

Main Methods:

• Employed precise microwave heating to achieve rapid, high-temperature glycosylations.
• Utilized both methyl 3,5-dinitrosalicylate (DISAL) and trichloroacetimidate glycosyl donors.
• Conducted reactions under neutral conditions, avoiding strong Lewis acid promoters.

Main Results:

• Achieved fast, high-temperature glycosylations in the synthesis of oligosaccharides.
• Demonstrated the efficacy of DISAL and trichloroacetimidate donors under microwave irradiation without Lewis acids.
• Successfully applied microwave heating as a general protocol for evaluating new glycosyl donors.

Conclusions:

• Microwave-assisted, high-temperature glycosylation offers a rapid and efficient alternative to conventional methods.
• This approach facilitates oligosaccharide synthesis under neutral conditions, broadening its applicability.
• The protocol is versatile for the evaluation of novel glycosyl donors, accelerating discovery in carbohydrate chemistry.