Methyl ulosonate,

Similar addition of other lithiated thio derivatives to substituted aldonolac-tones has been performed (69). Thus, reaction of tris(methylthio)methyl-lithium to benzylidenated or isopropylidenated aldonolactones, followed by mercury(II)-catalyzed desulfuration, led to derivatives of glyc-2-ulosonic acids. 

P. A. McNicholas, M. Batley, and J. W. Redmond, Synthesis of methyl pyranosides and furanosides of 3-deoxy-D-marcrco-oct-2-ulosonic acid (KDO) by acid-catalysed solvolysis of the acetylated derivatives, Carbohydr. Res., 146 (1986) 219-231. 

A new class of ald-2-ulosonic acids, 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acids, reported as sialic acids of a new type, was discovered in 1984.9 Members of this class contain an additional amino group at C-7, additional deoxygenation at C-9 (methyl group) and may exhibit configurational differences as compared with neuraminic acid. Unlike sialic acids, the new class of ald-2-ulosonic acids appears to be unique to microorganisms. 

Much effort towards stereoselective synthesis of 3-deoxy-2-ulosonic acids resulted in the development of several strategies based on the diverse building units. Among them aldol reaction between D-arabinose derivative 50 and methyl dichloroacetate (51) deserves some attention [78] (Scheme 14). The condensation product isolated as oxirane derivative 52 reacted smoothly with Mgk to give the intermediate 53, easily convertible into 3-deoxy-D-ara6mo-2-heptulosonic acid methyl ester 56 in high yield. 

Starting from D-gulonic-y-lactone the salt was formed and a 0.5 M solution converted to D-Jcy/o-hex-2-ulosonate sodium salt monohydrate in the same manner as described for the preparation of sodium D-araZ>/ o-hex-2-ulosonate. Part of it was converted to methyl-D-xy/o-hex-2-ulosonate, and this further to D-/Areo-hex-2-enono-1,4-lactone (D-ascorbic acid) as described (72). The H and C-NMR spectra in H20 are identical to those of an authentic sample of L-ascorbic acid. 

Acylation of methyl 3-deoxy-D-mflnno-oct-2-ulosonate leads to furanose derivatives, e.g. (15), while similar treatment of the free acid or its ammonium salt affords pyranoid products. Methanolysis of the ester gives mixed 5-membered... 

Two new syntheses of L-ascorbic acid have been reported, both giving methyl L-Jcy/o-hex-2-ulosonate (25) as immediate precursor. The first used D-glucurono-6,3-lactone (Scheme 5), whereas the second employed D-glucose and an initial bacterial oxidation step (Scheme 6). ... 

Deoxy-D-/Areo-hex-2-ulosonic acid has been synthesized by way of a Lewis acid catalysed ene reaction between methyl glyoxalate and l-/er/-butyldiphenylsi-lyloxy-but-3-ene." ... 

The isomeric forms of hexulosonic acids present in aqueous and other solutions have been studied by C n.m.r. methods. L-xy/o-Hexulosonic acid and its methyl ester exist predominantly in the a-pyranose form, whereas the D-arabino-isomers show a- and j3-pyranose and ot- and /3-furanose forms. The methyl ester favours the pyranoses in water and the furanoses in DMSO. D-xy/o-Hex-5-ulosonic acid showed both furanoses and the acyclic form, while this latter... 

Me ester, 3,4,5,6-tetra-Ac Methyl 3,4,5,6-tetra-O-acetyl-D-arahmo-hex-2-ulosonate... 

Tetra-Ac, Me ester Methyl 2,3,4,6-tetra-O-acetyl-D-xylo-hex-5-ulosonate [24916-35-6]... 

Methyl a-D-ga/flc o-hexodialdo-l,5-pyranoside, H-84 Methyl p-D-gfl/ac o-hexodialdo-l,5-pyranoside, H-84 Methyl a-D-g/wco-hexodialdopyranoside, H-85 Methyl p-D-g/wco-hexodialdopyranoside, H-85 Methyl a-L-g/wco-hexodialdopyranoside, H-85 Methyl p-L-g/wco-hexodialdopyranoside, H-85 Methyl a-D-xy/o-hexopyranosid-4-ulose 0-methyloxime, H-104 Methyl y.- D-arabino -hexopyranosid-2-ulose, H-94 Methyl p-D-xy/o-hexopyranosid-4-ulose, H-104 Methyl a-D-rj o-hexopyranos-3-uloside, H-101 Methyl D-flm6 w -hex-2-ulosonate, H-111 Methyl 3-0-(4-hydroxycinnamoyl)glycerate, D-709 Methyl 4-C-(hydroxyinethyl)-2,3-0-isopropylidene-p-D-eryf/iro-pentofuranoside, H-172... 

A chemicoenzymatic synthesis of l-dcoxy-D-xylo-bexose is discussed in Chapter 2, and the occurrence of 2-<9-methyl-6-deoxy-L-talose in an O-linked glycopeptide in Chapters 3 and 5. Syntheses of 2-deoxykanosamine and methyl a-D-evalopyranoside are mentioned in Chapters 9 and 14 respectively, and deoxyanalogues of ulosonic acids are covered in Chapter 16. 

Full details have been reported on the use of immobilized N-acetylneuraminate pyruvate lyase for the preparation of various 2-ulosonic acids, including KDN (see Vol. 21, p.160-161 and Vol. 23, p. 162).41 The IV-nitroso derivative (32) of NeuTVAc can be used as indicated in Scheme 10 to produce the peracetyl methyl ester (33) of KDN. Thermolysis of (32) gave alkene (34) together with the 4,5-ene and a ring-contracted product. Hydrogenation of (34) led to both the saturated compound and the hydrogenolysis product. ... 

Ramage and co-workers have given full details of their Wittig approach to 2-ulosonic acids (see Vol. 22, p.l61) and have extended this route to the synthesis of 3-deoxy-D-eryt/iro-2-hexulosonic acid (KDG, 30), albeit in low yield in this case.33 A French group have developed two routes to KDG (30) (Scheme 5) involving, respectively, a Wittig synthesis of (28) 4 or P elimination from a gluconolactone derivative to yield (29) 35 the second approach could be modified to make 5- and 6-(2-methyl ethers of (30). 

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