Dialdoses, preparation

Aldos-2-uk>ses, which have foe ketonic function at C-2, undergo mercaptaladon under the usual conditions, to afford only l,l-(dialkyl dithioacetal) derivatives. The ketone function in these compounds is distinctly unreactive toward thiols in acidic medium, probably as a consequence of electronic and steric effects [42] (Scheme 11). Examples of l,2-bis(dialkyl dithioacetal) derivatives have been prepared by indirect methods [43]. Dialdoses, on the other hand, in which the two carbonyl groups are separated by the sugar backbone, readily undergo mercaptalation at both carbonyl centers to afford bis(dialkyl dithioacetal) derivatives [44]. 

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... 

Application of the ring-closing olefin metathesis reaction (RCM) for the preparation of car-bocyclic rings from the appropriately functionalized sugars is now well documented [81]. Recently it was applied for the synthesis of compound 122, which can be regarded as a (n,m)-anhydrosugar [81]. The intermediate diolefin 121 was prepared in a few standard steps from the corresponding dialdose 120 (O Fig. 28) [82]. 

The first synthesis, that of eri/fftro-tetrodialdose, was made by Wohl and Mylo, starting from acetylene. The basis of the method employed (both here and in the further syntheses of this dialdose) is the hydroxylation of malealdehyde or a derivative of the latter. The next method introduced was Uenzelmann s application of catalytic reduction by the Rosenmund procedure to tetra-O-acetylmucyl dichloride he thus obtained the corresponding tetraacetate of gaZacto-hexodialdose. By this procedure, the only known heptodialdose has also been prepared. Another reduction procedure, controlled reduction of D-glucurono-6,3-lactone with borohydride or sodium amalgam, was used by MacDonald and H. O. L. Fischer and by F. G. Fischer and Schmidt. ... 

The Weerman degradation was employed in one of the first preparations of dialdoses, namely of n-f/ireo-tetrodialdose, using the diamide of D-glucaric acid as starting material. An inosose has been degraded to a pentodialdose by way of its disulfone and the Nef reaction, transformation of a 6-deoxy-... 

Clauson-Kaas and Fakstorp prepared the dialdose, isolated as the bis(phenylhydrazone), by the hydroxylation of furan. This reaction was performed with hydrogen peroxide/osmium tetraoxide in aqueous methanol and was expected, assuming 1,4-addition of the hydroxyl groups, to yield... 

Attempts to prepare the free dialdose by treating the bis(phenyl-hydrazone) with benzaldehyde were not successful. A crystalline compound Avith the analysis of a mono(phenylhydrazone) was isolated, however. After... 

Finally MacDonald and Fischer have prepared the free ajyZo-pento-dialdose (8) by the sulfone-degradation method. The diethyl dithioacetal of scyllo-inosose (12) was oxidized to the corresponding disulfone which, on treatment with ammonia, gave the dialdose (8). The structure was proved by converting the compound into the bis(ethylene dithioacetal) derivative, which was identical with that obtained from a /io-pentodialdose prepared by a previous method. ... 

The dialdose tetraacetate obtained was identical with that previously-prepared, and was further characterized by oxidation, with peroxypropionic acid, to tetra-O-acetylgalactaric acid. 

MacDonald and Fischer prepared D- fluco-hexodialdose (27) by two different methods. By use of the Nef reaction, 6-deoxy-l,2-0-isopropyli-dene-6-nitro-n-glucose (26) was converted into the dialdose (27), which was isolated from the aqueous solution as its insoluble, crystalline bis-(diethyl dithioacetal) (in 48% yield, after recrystallization). It is of interest to note that the starting material (26) is one of the two isomeric 6-deoxy-6-nitro sugars which Grosheintz and Fischer prepared from 1,2-0-iso-propylidene-a-D-x2/lo-pentodialdo-l, 4-furanose (7). Thus, the synthesis discussed here is an ascent from a pentodialdose to a hexodialdose. 

D-fiflwco-Hexodialdose and n-manno-hexodialdose have been reported to give crystalline bis (diethyl dithioacetal) derivatives, by the addition of ethanethiol to the dialdose dissolved in cold concentrated hydrochloric acid. The difficultly soluble dithioacetal readily precipitated after a short time. Similarly, the crystalline bis (ethylene dithioacetal) of xylo-pento-dialdose was prepared. A liquid bis(diethyl acetal) of erj/tliro-tetrodialdose and of the isopropylidene acetal of n-i/ireo-tetrodialdose " have also been reported. 

Papadakis also prepared some condensation products from the dialdose derivatives 1,2-0-isopropylidene-a-D-xj/lo-pentodialdo-l, 4-furanose (7) and... 

For many of the dialdehyde compounds which have been isolated, one or more of the standard carbonyl derivatives, for example, phenylhydra-zones, oximes, or semicarbazones, have been prepared. These have been described under the individual dialdoses. 

The Wittig reaction with dialdose derivatives has also been employed to synthesize polyols of long-chain hydrocarbons, as illustrated in Scheme 2 lyxose and xylose derivatives were similarly used to prepare stereoisomers which are relatives of naturally occurring plant products.- ... 

Several alkynes related to compound (29) were prepared by treatment of the corresponding dialdose derivative with alkynyl Grignard reagents, and by reduction and oxidation processes they were converted into a series of octose derivatives, e.g. reduction gave 7,8-dideoxy compounds and oxidation alkynyl glycos-6-uloses. ... 

Several compounds of the dialdose type (see formula, p. 299) have been prepared. Catalytic reduction of tetra-O-acetylgalactaric acid gave 2,3,4,5-tetra-O-acetyl-gfoZocto-hexodialdose 163). Lead tetraacetate oxidation of tetra-O-acetyl-myo-inositol, tetra-0-acetyl-a//o-inositol, and di-O-isopropyl-idene-D-inositol, respectively, gave the corresponding tdo-hexodialdose,... 

The treatment of a dialdose derivative with lithiated methyl phenyl sulphone is discussed in chapter 11, and the preparation of a synthon of deazatunicamycin is covered in chapter 19. An improved synthesis of (6- C) aldohexoses from 1,2-Q-isopropvlidene-q-D-xylo-pentodialdo-l.4-furanose is included in chapter 2. The racemic synthesis of an aminosugar dialdose is mentioned in chapter 9. 

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