Streptose synthesis

Stilbenes synthesis by Heck coupling, 43 Stille coupling aryl triflate + organylstannane, 42 Stobbe condensation, 58-59 Stork reagent, 328-329 Strain, steric. See Steric strain Strecker s synthesis of a-amino acids, 50, 301 L-Streptose synthesis, 267 Styrene. See Benzene, ethenyl-Succinic acid. See Butanedioic acid Succinimide. See 2,5-Pyrrolidinedione Sugars. See Monosaccharides Oligosaccharides inexpensive derivs. pr. (table), 263-264 Sulfafurazole, 307 Sulfamethoxazole, 308 Sulfenic acids, esters ... 

On the basis of the nuclear Overhauser effect, the cis arrangement of the methoxyl group on C-2 and in the side chain was established. The trans relationship of H-4 and H-5 was deduced from their coupling constant (/4>5 3.7 Hz). The post-hydroxylation mixture was shown to contain two other isomers of 317, as well as some of 318. The compounds were reported unsuitable for further transformation involving hydrolytic cleavage, as they polymerized readily in acidic media.205 This difficulty has been overcome in the following synthesis of racemic streptose tetramethyl acetal. 

Another synthesis of streptose derivatives has been completed in the authors laboratory. Among a number of oxetanes obtained from... 

H. Paulsen, V. Sinnwell, and P. Stadler, Synthesis of branched carbohydrates with aldehyde side-chains. Simple synthesis of L-streptose and D-hamamelose, Angew. Chem. Int. Ed. Engl. IT. 149 (1972). 

This methodology was applied to the synthesis of L-streptose [91] and methyl a-D-mycaroside [95 a], The difficulty of this photochemical oxidation originates from the sensitivity of pyruvates to hydrolysis. This approach seems limited to small quantities of substrates but does not need any separation technique as in oxidation by pyridinium chlorochromate [95 b]. Nethertheless, photolysis of pyruvates of partially protected derivatives of a-D-g/ucofuranose and P-D-fructofuranose in benzene yields the corresponding oxidized products in excellent yields [96]. 

Several compounds of this type, formally derived from aldoses by oxidation of the terminal CH2OH group to -CHO, have been prepared. Dialdoses arise as intermediates in structural studies, but they are also valuable starting materials for synthetic conversions, in particular for natural-product synthesis. A branched-chain dialdose, streptose (167), occurs as a component of the antibiotic streptomycin. The structure of streptose was elucidated after extensive investigations of its derivatives and transformation products.371 The 2,5-dimethoxytetrahydrofuran fulvanol (168), an analogue of apiose, has been isolated from the plant Hemerocallis fulva 12... 

A chain-elongation reaction was used for the synthesis of streptose (167) starting from 5-deoxy-l,2-0-isopropylidene-j6-L-tAreo-pentofuranos-3-ulose (185).387... 

In experiments in which sodium borohydride was added to the enzyme incubation mixture of the apiose/xylose synthase, no reduction products could be found that would arise from epimerization at C-3 of the 4-ketose intermediate.44 In the synthesis of apiose, ring contraction therefore seems to take place with the L-threo-pentos-4-ulose 27 (see Scheme 11), and not with the L-erythro intermediate, which would be analogous to the ring contraction in the biosynthesis of L-dihydro-streptose. 

In addition to the functionalization protocols of Schemes 13 and 14, vinylic substitution reactions involving metalation and palladium-mediated carbon-carbon bond formation have been formulated," which further broaden the variety of stmctural types available from the Patemo-BUchi reaction. For example, deprotection and stannylation of photoaldol (133), followed by refimctionalization of the a-enol ether position of vinylstannane (134), gave the substituted oxetane (135) in good overall yield. Similar functionalization of bicyclic oxetane (136) via exo-face dihydroxylation and acid-catalyzed reorganization of the acetal to the protected 3-deoxy-( )-streptose (137) has been reported, which illustrates the synthetic utility of such processes in the synthesis of polyoxygenated materials." ... 

L-Streptose 2-Lilhio-1,3-dithiane has been used in the synthesis of branched sugars with aldehyde or keto groups in the side chain. The reaction sequence is illustrated for the synthesis of L-streptosc (4) from the 3-ulose (1). The most critical step is the... 

Whereas streptidine and 2-deoxy-2-(methylamino)-L-glucose, components of streptomycin, were synthesized by 1950, some fifteen years elapsed before the synthesis of streptose was achieved by Dyer and coworkers. Another synthesis of streptose was reported by Paulsen and coworkers. The glycosidic linkage between streptose and 2-deoxy-2-(methylamino)-L-glucose had previously been shown to be a-L, and the glycosidic linkage between streptose and streptidine has been revised to be o-L on the basis of n.m.r.-spectral studies. ... 

T. Kofluk and A. Zamojski, Hydroxylation of 6-substituted 2,7-dioxabicydo[3.2.0]hept-3-enes. The synthesis of analogs of 3-deoxy-DL-streptose," Collect. Czech. Chem. Commun., 48, 1659... 

Further modifications of dihydrostreptose to streptose or S -hydroxystreptose seem to occur on the final condensation products only (cf. Section V.E), rather chan during synthesis of the dTDP-activated precursor. The 5 -hydroxy-group in antibiotic produced by S. glaucescem is unlikely to stem from the original D-glucose, since then the three enzymes StrE, StrM, and StrL would need to have acquired new substrates and even a new reaction mechanism in the case of the dTDP-o-glucose 4,6-dehydratase. 

Paulsen s group has transformed the protected streptosyl chloride (or bromide) (521 RS = Ph,H) into dihydrostreptosylstreptidine (522) and related pseudo-disaccharides. ° ° The 2,3-0-benzylidene derivatives (521 R R = Ph,H) yielded a-linked glycosides of L-streptose preferentially, whereas the 2,3-carbonates (521 R R = O) gave / -linked glycosides e.g. with cyclohexanol and l,2,3,4-tetra-0-acetyl-)5-D-glucopyranose). ° This work culminated in the synthesis of D-streptobiosamine (523) and its L-enantiomer (a disaccharide unit of streptomycin) by a route that involved condensation of methyl a-o(or L)-strepto-side 3 -(trimethylene dithioacetal) with the nitrosyl chloride adduct of 3,4,6-tri-O-acetyl-D-(or L)-glucal. ... 

An interesting synthesis of 3-deoxy-DL-streptose utilized the dioxabicycloheptene (30) obtained by cycloaddition of furan and ethanal stereospecific exo-cis-hydroxylation was accompanied by C-3 epimerization, giving a mixture resolved into the deoxy-... 

Bromo-2-deoxy-sugars, derived from glycals, can be photo-chemlcally converted into 2-deoxy-sugars on irradiation in 2-propanol thus compound (13) was obtained from bromide (1 ). Photolytic de-iodination was utilized in a synthesis of L-streptose (Chapter 13). 

A synthesis of L-streptose from L-arabinose has been described... 

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