Glyceraldehyde optical activity

HC CH(0H) CH20H. optically active. D-glyceraldehyde is a colourless syrup. May be prepared by mild oxidation of glycerol or by hydrolysis of glyceraldehyde acetal (prepared by oxidation of acrolein acetol). DL-glyceraldehyde forms colourless dimers, m.p. IBS-S C. Converted to methylglyoxal by warm dilute sulphuric acid. The enantiomers... 

As shown for the aldotetroses an aldose belongs to the d or the l series accord mg to the configuration of the chirality center farthest removed from the aldehyde func tion Individual names such as erythrose and threose specify the particular arrangement of chirality centers within the molecule relative to each other Optical activities cannot be determined directly from the d and l prefixes As if furns ouf bofh d eryfhrose and D fhreose are levorofafory buf d glyceraldehyde is dexfrorofafory... 

Fischer s Convention. Initially, the absolute configurations of optical isomers were unknown to chemists working with optically active compounds. Emil Fischer, the father of carbohydrate chemistry, decided to relate the possible configurations of compounds to that of glyceraldehyde of which the absolute configuration was yet unknown but was defined arbitrarily. 

Since the starting materials are available by reaction of aldehydes with lithiated vinyl ethers, this sequence is useful for conversion of aldehydes into these triols. Indeed this sequence can be used to convert an optically active glyceraldehyde into optically pure pentitols with high syn-stereocontrol. 

The presence of an asymmetric carbon atom confers the property of optical activity on the molecule, enabling it to cause the rotation of a beam of plane polarized light in either a clockwise or an anticlockwise direction. Thus all naturally occurring carbohydrates containing asymmetric carbon atoms are optically active and can be designated (+) for clockwise (dextro) rotation or (-) for anticlockwise (laevo) rotation. The designation of d or l to glyceraldehyde, the simplest monosaccharide, which has only one asymmetric centre, refers to... 

Let us look at the example of glyceraldehyde, an optically active molecule. Glyceraldehyde can exist as enantiomers, i.e. (- -) and (—) forms, hut the sign does not describe the exact configuration. 

All the monosaccharides except dihydroxyacetone contain one or more asymmetric (chiral) carbon atoms and thus occur in optically active isomeric forms (pp. 17-19). The simplest aldose, glyceraldehyde, contains one chiral center (the middle carbon atom) and therefore has two different optical isomers, or enantiomers (Fig. 7-2). 

OPTICAL ISOMER- Either of two kinds of optically active three-dimensional isomers (stereoisomers). One kind is represented by mirror-image presence of one or more asymmetric carbon atoms in the compound (glyceraldehyde, lactic acid, sugars, tartaric add, amino acids). The other kind is exemplified by diastereoisomers, which are not mirror images. These occur in compounds having two or more asymmetric carbon atoms thus, such compounds have 2 optical isomers, where n is the number of asymmetric carbon atoms. 

Chiral imines have been prepared by reacting (R)-glyceraldehyde acetonide with different co-haloalkylammonium halides. Treatment of the latter with 1.3 equiv. of benzyloxy-, phenoxy- or methoxy acetyl chloride in dichloromethane, in the presence of triethylamine afforded the optically active corresponding (3-lactams (Scheme 38) in high yield and high diastereomeric excess [113]. 

Benzotriazoles derived from anilines and (f )-glyceraldehydes dissociate in the presence of Sml2 and undergo cycloaddition to give the optically active tetrahydroisoquinoline (Scheme 77) <2000JOC3148>. 

Whereas glyceraldehyde has one chiral center, aldotetroses, -pentoses, and -hexoses have two, three, and four, respectively. Each chiral center gives rise to optical activity. The net optical activity of an aldose will depend on contributions from each chiral center and will be (+) or (-). 

Baer, E., and Fischer, H. O. L. 1941. Studies on acetone-glyceraldehyde, and optically active glycerides. J. Biol. Chem., 40, 397 110. 

Optically active L-glyceraldehyde can be obtained biocatalytically by use of a D-specific ADH. This enzyme reduces the D-enantiomer yielding glycerol and enantiopure L-glyceraldehyde (Fig. 41). NADPH as the coenzyme for the reduction was regenerated by GDH. 

Optically active C3-building blocks of type 1 are key starting compounds in organic synthesis.6 The most important member of this class is 2,3-O-isopropylidene-glyceraldehyde 2.67... 

The two glyceraldehyde isomers of 4-13 are identical in all physical properties except that they rotate the plane of polarized light in opposite directions and form enantiomorphous crystals. When more than one asymmetric center is present in a low-molecular-weight species, however, stereoisomers are formed which are not mirror images of each other and which may differ in many physical properties. An example of a compound with two asymmetric carbons (a diastereomer) is tartaric acid, 4-16, which can exist in two optically active forms (d and L, mp 170 C), an optically inactive form (meso, mp 140 C), and as an optically inactive mixture (dl racemic, mp 206°C). 

Both exo- and endo-brevicomin vide infra), in optically active form, have been synthesized by elaboration of a-alkoxy aldehyde (201). Condensation of the 1-trimethylsilylvinylcopper reagent (198) with the ( )-glyceraldehyde derivative (199) gave syn product (200) in >85% yield with over 98% dia-stereoselectivity (Scheme 36). Hydroxy protection, hydrolysis and periodate cleavage of the vtc-diol converted (200) to aldehyde (201) in 50-65% overall yields for the two steps. 

Reaction of lithiodithianes with acyl chlorides, esters or nitriles leads to the fOTination 1,2-dicarbonyl compounds in which one of the carbonyl groups is protected as the thioacetal. d76043j44 Optically active amino ketones of type (69) are inepared via acylation of dithiane with an oxazoline-protected (5)-serine methyl ester (Scheme 41). Optically active (5)-2-alkoxy-l-(l,3-dithian-2-yl)-l-propanones were prepaid by the reaction of the corresponding methyl (5)-lactate with 2-lithio-l,3-enantioselective synthesis of (-)-trachelanthic acid. Enantioselective synthesis of L-glyceraldehyde involves the acylation of a dithiane glycolic acid derivative followed by bikers yeast mediated reduction. ... 

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