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Alternatives include carbonyl allylation with allylmetallic reagents, such as allyltrimethylsilane, [9] [10] [11] or the iridium-catalyzed Krische allylation. Allylation can be effected also by conjugate addition: the addition of an allyl group to the beta-position of an enone. The Hosomi-Sakurai reaction is a common method for conjugate ...
The single-molecule (monomer) catechin, or isomer epicatechin (see diagram), adds four hydroxyls to flavan-3-ol, making building blocks for concatenated polymers (proanthocyanidins) and higher order polymers (anthocyanidins). [2] Flavan-3-ols possess two chiral carbons, meaning four diastereoisomers occur for each of them.
Glycoproteins have distinct Oligosaccharide structures which have significant effects on many of their properties, [11] affecting critical functions such as antigenicity, solubility, and resistance to proteases. Glycoproteins are relevant as cell-surface receptors, cell-adhesion molecules, immunoglobulins, and tumor antigens. [12]
Secondary structure refers to highly regular local sub-structures on the actual polypeptide backbone chain. Two main types of secondary structure, the α-helix and the β-strand or β-sheets, were suggested in 1951 by Linus Pauling. [5] These secondary structures are defined by patterns of hydrogen bonds between the
The term "2-deoxyribose" may refer to either of two enantiomers: the biologically important d-2-deoxyribose and to the rarely encountered mirror image l-2-deoxyribose. [3] d-2-deoxyribose is a precursor to the nucleic acid DNA. 2-deoxyribose is an aldopentose, that is, a monosaccharide with five carbon atoms and having an aldehyde functional group.
The carbohydrate part of the molecule is called glycone, the -O- bridge is the glycosisdic oxygen, and the attached group is the aglycone. Glycosides are named by giving the aglyconic alcohol HOR, followed by the saccharide name with the '-e' ending replaced by '-ide'; as in [[phenol D -glucopyranoside]].
A disaccharide (also called a double sugar or biose) [1] is the sugar formed when two monosaccharides are joined by glycosidic linkage. [2] Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, lactose, and maltose.
The easiest way to visualize the mechanism of a step-growth polymerization is a group of people reaching out to hold their hands to form a human chain—each person has two hands (= reactive sites). There also is the possibility to have more than two reactive sites on a monomer: In this case branched polymers production take place.