Sugars synthetic application

The KDO aldolase (KdoA, EC 4.1.2.23) is involved in the catabolism of the eight-carbon sugar d-KDO, which is reversibly degraded to D-arabinose (15) and pyruvate (Figure 10.10). The enzyme has been partially purified from bacterial sources and studied for synthetic applications [71,74]. It seems that the KdoA, similar to... 

This chapter includes the most relevant recent contributions to the preparation and synthetic applications in nitro sugar chemistry. 

Further Synthetic Application of the "Naked Sugars" Total Synthesis of Nonactin... 

The enzymatic approach to the synthesis of carbohydrates and their precursors is practical for certain types of sugars. The next stage of our investigation will be to focus on the modification of these readily available sugars to agents of interest. Improvement of enzyme properties for synthetic application is also of interest. 

Another useful synthetic application of a Diels-Alder adduct of the chloro ester 1-Me is the facile preparation of the spirocyclopropanated analog 75 of so-called naked sugar 76 [50] (Scheme 19) [30]. The transformation of the adduct endo-59a of 1-Me onto furan (57) into a-chloroamide 74 followed by fragmentation of the latter under basic conditions allowed to prepare the versatile building block 75 in 71 % overall yield. Starting from isomer exo-59a, the yields were 82 and 52% for the first and the second step, respectively. The analogous trans-... 

Three types of lyases have been identified that catalyze the addition of phosphoenolpyruvate (PEP) to aldoses or to terminally phosphorylated sugar derivatives. With simultaneous release of inorganic phosphate from the preformed enolpyruvate nucleophile during C-C bond formation the additions are essentially irreversible and, therefore, these lyases are often referred to as synthases. The mechanistic details of these reactions, however, have yet to be elucidated but it seems obvious that the chances of variation on the part of the nucleophile will be strictly limited. Although the thermodynamic advantage makes these enzymes highly attractive for synthetic applications, none of them is yet commercially available and only few data have been reported concerning the individual specificities towards aldehydic substrates. 

N. K. Kochetkov and A. F. Bochkov, Sugar orthoesters and their synthetic applications, in R. Bognar, V. Druckner, and S. Szantay (Eds.), Recent Developments in the Chemistry of Natural Carbon Compounds, Vol. 4, Akad. Kiado, Budapest, 1971, pp. 77-192. 

The literature has been reviewed through 1989 for the purposes of preparing this chapter but the documentation herein is not intended to be comprehensive. Other reviews have covered various aspects of asymmetric epoxidation including synthetic applications through 1984, a thorough compilation of uses through early 1987 and an extensive discussion of the mechanism of the reaction. Use of homochiral epoxy alcohols in the synthesis of polyhydroxylated compounds, e.g. sugars, and for the preparation of various synthetic intermediates has been reviewed.A personal account of the discovery of titanium-catalyzed asymmetric epoxidation has been recorded." A comprehensive review of titanium-catalyzed asymmetric epoxidation is planned."... 

It follows from the above that, if highly specific oligosaccharides need to be synthesized, glycosyltransferases [21] of the Leloir type [22] should be the enzymes of choice. These enzymes connect sugars via the activated nucleotide components with high stereo- and regioselectivity. They are substrate-specific, but, in vitro, with solubilized enzymes, it becomes possible to transfer modified donors to modified acceptors and thus broaden the scope of the synthetic applicability. 

This chapter is exclusively devoted to the occurrence, significance, and physical and randomly selected chemical properties of various groups of sugars and their implications in synthetic applications of these specified classes of monosaccharides. 

GAOX stereospecifically oxidizes a broad range of substrates (Table 16.2-9). In synthetic applications, the oxidation of racemic or meso-polyols such as D,L-threitol or xylitol to the non-native sugars are of special interest1151, 152l In addition to the monosaccharides represented in Table 16.2-9, GAOX also converts di- or oligosaccharides 1531. 

Mechanistic Aspects of Anhydro Sugar Polymerization Related to Polymer Structure and Synthetic Applications... 

The crystalline product (45b) is stable for several days at room temperature. It is unusual in being a thio sugar derivative in which the sulfur atom is electrophilic in character, and it offers possibilities for novel synthetic applications. ... 

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