Heptuloses preparation

LaForge and Hudson194 prepared an osone from the phenylosazone obtained from sedoheptulose (D-aZ(ro-heptulose). The osone reduced Fehling solution strongly, formed the original osazone with phenylhydrazine, and gave a crystalline derivative with o-phenylenediamine. 

D-afe-o-Heptulose (sedoheptulose) (XXXVII) has been synthesized from D-erythrose (XXXVIII) plus triose phosphate, using an aldolase preparation from peas.169 Aldolases from yeast and from rat liver also form heptu-lose phosphate from these substrates.7S(o) 170(a) Crystalline muscle aldolase causes the formation of L-jrZwco-heptulose (XXXVIIa) from a mixture of L-erythrose (XXXVTIIa) and hexose diphosphate.170(b)... 

The above transketolase and transaldolase reactions were found inadequate to explain the metabolism of D-ribose 5-phosphate, because of the non-accumulation of tetrose phosphate, the 75 % yield of hexose phosphate, and the results of experiments with C14 (the distribution of which differed markedly from the values predicted for such a sequence). 24(b) Thus, with D-ribose-l-C14, using rat-liver enzymes, any hexose formed should have equal radioactivity at Cl and C3, whereas, actually, 74% appeared at Cl. Furthermore, D-ribose-2,3-Cl42 should have given material having equal labels at C2 and C4 in the resultant hexose, whereas, in fact, it had 50% of the activity at C4, C3 was nearly as active as C2, and Cl had little activity. Similar results were obtained with pea-leaf and -root preparations.24 The following reactions, for which there is enzymic evidence,170(b) were proposed, in addition to those involving D-aftro-heptulose, to account for these results.24(b) (o) 200... 

Like nitromethane, 2-nitroethanol can be used as the methylene component for addition to aldehydes, giving epimeric nitrodiols in which the carbon chains have been lengthened by two carbon atoms. This reaction has attained preparative importance for the S5mthesis of higher-carbon ketoses 43,44) heptulose-phosphates 5) and of chloramphenicol... 

This enzymically prepared product was, therefore, tested with bacterial extracts. Almost quantitative conversion to shikimate took place. Furthermore, D-olheptulose diphosphate labeled in carbon atoms 4,5,6, and 7 with C, prepared from uniformly labeled D-oZiro-heptulose 7-phosphate and unlabeled n-fructose diphosphate (see Fig. 3), was converted to shikimate labeled exclusively in carbon atoms 3,4,5, and 6. It is clear, however, that a cyclization of the intact carbon-chain of D-aZtriose phosphate isomerase, carbon atoms 1,2, and 3 of the heptulose diphosphate would be derived from G-(l,6), G-(2,5), and G-(3,4), respectively. Carbon atoms 7,1, and 2 of shikimate, as discussed previously (see Fig. 1), are derived from the reverse sequence, namely, G-(3,4), G-(2,5), and G-(l,6). Apparently, carbon atoms 1,2, and 3 of the heptulose diphosphate become detached, and their order is reversed, before their incorporation into shikimic acid. 

The reported yields in these ketose preparations range from less than 10% to around 50%. Nevertheless, this is the method of choice for preparing certain ketoses, especially where the starting aldose can be sacrificed. For some unknown reason, the best yields have consistently been obtained in the formation of D- Zwco-heptulose from D-j/Zj/cero-D-j/aZo-heptose. The procedure of Pratt, Richtmyer, and Hudson for preparation of this substance is given here. 

Although these syntheses of deoxy ketoses have not been widely developed, the versatility of diazomethane as a synthetic reagent is amply demonstrated. In addition to heptuloses, the diazomethane method has been used for preparing various octuloses " and nonuloses. ... 

Two 3-heptuloses have been synthesized n-wianno-S-heptulose was prepared by degradation of a branched-chain octose, and a related... 

Occurrence and preparation. D-aZZro-3-Heptulose (coriose) is the first clearly characterized 3-heptulose found in a natural product. This 3-heptulose was obtained from chromatographed extracts of the roots of Primula officinalis Jacq256 (see under D-gZycero-D-gZwco-heptose), and it has also been isolated from the leaves... 

L. Stankovic and V. Bilik, Occurrence and preparation of D-wuumo-heptulose, Chem. Listy, 80 (1986)520-527. 

A thioglycoside containing a second ethylthio group, of unknown location, was prepared from hexa-O-acetyl-D- lwco-heptulose by the action of ethanethiol in the presence of zinc chloride. 

Crystalline 5,7-O-ethylidene acetals of feeto-D-monno-heptulose (111) and D-a/fro-heptulopyranose (112) have been prepared by... 

Azido-sugars are frequently prepared by reaction of epoxides with azide ion. 3-Azido-3-deoxy-L-threose 68 was synthesized from cu-but-2-ene-l,4-diol 66 via the Sharpless asymmetic epoxidation product 67, and was converted into 6-azido-6-deoxy-L-galocro-heptulose 69 by an enzyme-catalyzed aldol condensation (Scheme 13). 3-Azido-3-deoxy-L-etythrose, and thence 6-azido-6-deoxy-L-g/uco-heptulose were obtained in a similar way via 4-rerf-butyldiphenylsilyoxy-rraiu-but-2-enal. These and two other azido-heptulose isomers made from the enantiomeric 3-azido-3-deoxy-tetroses, were converted to a- and P-l-homonojirimycin and homomannonojirimycin on hydrogenation. Ethyl 3-azido-2,3-dideoxy-D-eryr/iro-pentopyranoside and its 3-C-methyl analogue 71, R=H or Me, were synthesized from crotonaldehyde or 3-methyl-2-... 

The structure of nogalamycin, an antibiotic containing the branched-chain sugar nogalose, and that of o-hamamelose in solution are mentioned in Chapters 18 and 20, respectively. The preparation of an unusual trihalogenated, branched-chain heptulose (147) from xylaric acid has been discussed in Chapter 7. 

Preparation (116). Ground avocados are extracted with water and the extracts evaporated to a thick sirup from which the sugar and perseitol are extracted with alcohol. The process may be repeated several times. The perseitol crystallizes from the alcoholic solution and the D-manno-heptulose is separated as the p-bromophenylhydrazone, which is converted to the sugar by treatment with benzaldehyde. When crystals are once available, the sugar may be crystallized directly from the extracts. 

D-manno-Heptulose also may be prepared readily from D-arabinose by the nitroethanol synthesis (see p. 111). 

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