Sugar absolute configuration

Sugar absolute configuration, 3242 Sugars, 1807, 2108, 2837 Suicidal germination, 3597 Sulfatation, 2397 Sulfenic acids, 3666, 3674 Sulfhydryl, 3674 N-Sulfocarbamoyl, 63 N-Sulfocarbamoyl toxins, 54, 55 Sulfotransferase, 2475... 

The absolute configuration of (—)-29 was established by X-ray crystal structure analysis of the bromolactone (89), which was prepared from (—)-29 by bromolactonization with hypobromous acid. It was found that ( )-29 belongs to the d series of carba-sugars, and hence, (+)-29 corresponds to the L series. - ... 

The different methylated sugars known as components of bacterial polysaccharides are summarized in Table 1. When possible, references to publications in which the methylated sugar is part of a known structure are preferred to references in which the component has merely been identified. References to sugars of undetermined configuration or absolute configuration have been omitted when there is reason to assume that they are identical to better characterized compounds from other sources. 

Stoichiometric enantioselective addition of lithium aluminum hydride, modified with ( — )-men-thol or sugar derivatives as chiral auxiliaries to enynols provides an entry to /Thydroxyallenes of low enantiomeric purity117 119. This method has mainly been used to establish absolute configurations of naturally occurring allenes, e.g., (—)-marasin119, and has not been optimized. 

By convention, one of these two forms is designated the d isomer, the other the l isomer. As for other biomolecules with chiral centers, the absolute configurations of sugars are known from x-ray crystallography. To represent three-dimensional sugar structures on paper, we often use Fischer projection formulas (Fig. 7 2). 

Arabinose—as could be shown by chain extension and degrading of glucose and mannose—forms a portion of both of these hexoses its configuration can be neither that of ribose, nor that of xylose, because, in contrast to arabinose, these pentoses form inactive dicarboxylic acids. The formula (7) (lyxose) is ruled out for arabinose, since a one-carbon addition to it leads to an inactive (galactaric) acid and an active (talaric) acid. Consequently, D-arabinose must have formula (5) and with that conclusion, (10) had been derived for D-(+)-glucose—but with one restriction. Fischer had to choose between (10) and its enantiomorph he chose (10), and wqs aware of the arbitrary nature of this decision. The same decision fixed the form of all the other series-related sugars represented in Fig. 1. That Fischer had accidentally chosen the correct absolute configuration was not realized until after his death. 

The d and L-sugars and amino acids are enantiomorphs and differ in absolute configuration about every asymmetric carbon atom. The pentose L-arabinose is structurally related to the sweet-tasting hexose, D-galactose, and, to recognize this, we predicted (2) that L-arabinose would probably taste sweet. 

A serious ambiguity arises for compounds such as the active tartaric acids. If the amino-acid convention is used, (+)-tartaric acid falls in the d series by the sugar convention, it has the l configuration. One way out of this dilemma is to use the subscripts, v and g to denote the amino-acid or carbohydrate conventions, respectively. Then the absolute configuration of (+)-tartaric acid can be designated as either Ds-(+)-tartaric acid of lb-(+)-tartaric acid. 

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