Mechanistic evidence observed in Hofmann-Löffler-Freytag-type reactions has been crucial to achieve the chemoselective functionalization of methyl groups under mild conditions. Radical-mediated methyl iodination and subsequent oxidative deiodination are the key steps in this functionalization, where iodine chemistry has a pivotal role on the formation of the C-N bond. The concepts of single hydrogen atom transfer (SHAT) and multiple hydrogen atom transfer (MHAT) are introduced to describe the observed chemoselectivity.

Photolysis of 1-glycosyl-2,3-butanodione derivatives using visible light is a mild and selective procedure for the synthesis of chiral 1-hydroxy-1-methyl-5-oxaspiro[3.5]nonan-2-one carbohydrate derivatives. The results strongly suggest that stereocontrol of the cyclization is dependent on conformational and stereoelectronic factors. Further oxidative opening of the 1-hydroxy-1-methyl-2-cyclobutanone moiety affords new C-ketoside derivatives either in C- and O-glycoside series. This tandem two-step process could be considered to be a stereocontrolled 1,3-transference of an acetyl group, and it can be applied either to pyranose and furanose models.

Water is indispensable for the life of any organism on Earth. Consequently, osmotic stress due to salinity and drought is the greatest threat to crop productivity. Ongoing climate change includes rising temperatures and less precipitation over large areas of the planet. This is leading to increased vulnerability to the drought conditions that habitually threaten food security in many countries. Such a scenario poses a daunting challenge for scientists: the search for innovative solutions to save water and cultivate under water deficit. A search for formulations including biostimulants capable of improving tolerance to this stress is a promising specific approach. This review updates the most recent state of the art in the field.

The stereochemical and conformational factors controlling the intramolecular hydrogen-atom transfer (HAT) reaction between the two pyranose units in a (1-->4)-O-disaccharide when promoted by a primary 6-O-yl radical are studied. Models with alpha-D-Glcp-(1-->4)-beta-D-Glcp, alpha-L-Rhamp-(1-->4)-alpha-D-Galp or alpha-D-Manp-(1-->4)-beta-L-Gulp skeletons led exclusively to the abstraction of the hydrogen from H--C-5' and the formation, through a nine-membered transition state, of a 1,3,5-trioxocane ring system in a stable boat-chair conformation. Notwithstanding, derivatives of alpha-L-Rhamp-(1-->4)-alpha-D-Glcp or alpha-D-Manp-(1-->4)-alpha-D-Galp exclusively abstract the hydrogen from H--C-1' through a seven-membered transition state and, therefore, lead to an interglycosidic spiro ortho ester.

A nine‐membered transition state characterizes the regioselective abstraction of the proton at C5′ that leads to the orthoacetate 2 as the product. The alkoxy radical intermediate is obtained from the Glc‐α1→4‐Glc derivative 1 with (diacetoxyiodo)benzene (DIB) and iodine. A similar 1,8‐hydrogen abstraction results when the alkoxy radical intermediate is generated under reductive conditions.