Synthesis of the Sugars

Complete Synthesis of the Sugars a. Formose and Related Products 

Formaldehyde condenses in the presence of weak bases to form a complex mixture of sugars called formose or methose The polymerization undoubtedly proceeds through a combination of acyloin and aldol condensations. Fischer and Tafel 125) obtained a similar sugar mixture by the action of dilute alkali on acrolein dibromide. Presumably, the reaction sequence is the following (Chapter I)  

Treatment of the reaction product with phenylhydrazine gave two crystalline hexosazones in yields of about 13% 125, 126). The two osazones were 

Fischer and Tafel s Complete Synthesis of Hexose Sugars a-ACROSE (from formaldehyde, glyceraldehyde, or acrolein dibromide) c H6NHNH2 

A further discussion of the aldol condensation as a synthetic method for the sugars appears on page 113. 

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The reaction catalyzed by ADPGlc PPase is reversible, and it should be noted that regulatory properties can be different in the two directions. For example, pyrophosphorolysis is usually much less affected by allosteric activators than is the synthesis of the sugar nucleotide (e.g., see Ghosh and Preiss, 1966 Preiss et al., 1967). 

More recently, Wolfrom and Foster found that the d and l enantio-morphs of methyl 3,4-0-isopropylidene-2-0-[(methylthio)thiocarbonyl]-/3-arabinop3Tanoside rearrange, on pyrolysis, to the appropriate 2-methyl-thio)carbonyl] esters. The reductive desulfurization of methyl 3,4-0-isopropylidene-2- S - [(methylthio)carbonylj - 2 - thio -/3 - d - arabinopyranoside (LXVIII) with Raney nickel, to afford a low yield of methyl 2-deoxy-3,4-0-isopropylidene-/3-D-erj/intramolecular rearrangement to LXVIII, and the relationship of the transformation to the Chugaev reaction was discussed. 

Longer chain isoprenoids are synthesized via two other isoprenyl diphosphate enzyme systems in mammals [21]. Long E-isoprenyl diphosphate synthase (IDS) produces the side chains of ubiquinone. The length of the side chain varies amongst species, and in humans a C50 synthase has been identified [22]. Dehydrodolichyl diphosphate synthase, the only Z-IDS found in mammals, is responsible for the synthesis of the sugar carriers dohchol and dolichyl phosphate [23]. Plants have additional Z-IDS which can catalyze the production of very long isoprene species, such as natural... 

Like Gaul, the synthesis of the anthracyclines is divided into three parts construction of the aglycones (e.g.,adrlamycinone, lb, daunomycinone, 2b, or carminomyclnone, 3b), synthesis of the sugar residue and coupling of the two. 

Synthetic polymers containing sugar branches have attracted considerable interest in recent years. These are typically produced via chemoenzymatic routes where the first step is the enzyme-mediated synthesis of the sugar ester monomer followed by chemical polymerization (Scheme 2). Several workers have developed sugar ester-abased polymers containing vinyl, styrene, acrylamide, etc., functionalities. A discussion of the synthesis methods of these compounds are not in the scope of the current work and interested readers are referred to some recent literature by Patil et al. [64], Kitagawa and Tokiwa [65], and Raku and Tokiwa [66]. 

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