Inosose

Although a bicyclic hemiacetal form such as XXXII is sterically possible, Posternak considered, in view of its unusual reducing power, ready reduction and ultraviolet absorption characteristics, that the keto form XXXI is more probable. 

The question of the configuration of epi-meso-inosose has recently been answered by Posternak. Examination of the formula for meso-inositol (V) will reveal that oxidation might give rise to six inososes. Attack at the equivalent positions one and three would give the enantio-morphous pair of inososes (XXXIII and XXXIV). In precisely the same manner, oxidation of carbons four and six would give the enantio-morphous pair XXXV and XXXVI. On the other hand, oxidation at either position two or five would result in the formation of the sym- 

L-talomucic and D,L-glucosaccharic acids. epi-meso-Inosose is therefore the racemate represented by XXXIII and XXXIV while the reduction product epi-inositol is II, representing as it does, an inversion of 

Both Chargaff and Magasanik as well as Posternak have shown that cpi-inositol is oxidized by Acetobacter suboxydans to a levorotatory inosose. Postemak found that reduction of this compound with sodium amalgam in acid solution gives a mixture of meso-inositol and cpf-inositol, proving that the substance is one of the enantiomorphs XXXIII or XXXIV. Since oxidation with permanganate afforded D-talomucic and D-glucosaccharic acids, the levorotatory cpf-meso-inosose must be represented by XXXIII. 

As mentioned earlier, meso-inositol, and indeed all the inositols, are readily converted to aromatic compounds by oxidation. Posternak found that inosose has the tendency to form phenolic compounds under very mild conditions. On attempted acetylation of inosose with acetic anhydride in the presence of either pyridine or sodium acetate the expected pentaacetate was not obtained the product was 1,2,3,5-tetra-acetoxybenzene (XXXVII). Similarly, the treatment of inosose pentaacetate with boiling acetic anhydride and pyridine or sodium acetate gave the same product. Inosose pentabenzoate was prepared by the use of benzoyl chloride and zinc chloride. Under the influence of pyridine or sodium acetate in acetic acid the pentabenzoate lost two molecules of benzoic acid to give l-hydroxy-2,3,5-tribenzoxybenzene (XXXVIII). 

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Success finally resulted when the inosose ether (20) was converted to its ethylene mercaptal. The crude mercaptal was reduced with nickel, and the crude pentol pentamethyl ether cleaved in the usual manner. 

Quebrachitol was converted into iL-c/j/roinositol (105). Exhaustive O-isopropylidenation of 105 with 2,2-dimethoxypropane, selective removal of the 3,4-0-protective group, and preferential 3-0-benzylation gave compound 106. Oxidation of 106 with dimethyl sulfoxide-oxalyl chloride provided the inosose 107. Wittig reaction of 107 with methyl(triphenyl)phos-phonium bromide and butyllithium, and subsequent hydroboration and oxidation furnished compound 108. A series of reactions, namely, protection of the primary hydroxyl group, 0-debenzylation, formation of A-methyl dithiocarbonate, deoxygenation with tributyltin hydride, and removal of the protective groups, converted 108 into 7. 

A more unusual monoepoxidation was observed when l-halo-l,3-cyclohexadienes were treated with aqueous solutions of potassium permangnate35. Oxidation of 18 resulted in formation of the unusual halo-epoxydiol 19 as the major oxidation product (equation 19). Hydrolysis of 19 with water in the presence of AI2O3 afforded the rare inosose 20 in high yield. 

The General myo-lnositol and scyllo-Inosamine Pathway. Two distinct cyclitol pathways, which we earlier called Ca (started by myo-inositolphos-phate synthase) and Cb (started by T-deoxy-i cy/to-inosose synthase), are used in the initiation of AGA pathways. Here we will describe the Ca route and the Cb pathway in the paragraph on NEOs (see Section 2.2.2.1.3). The cyclitol pathway in the biosynthetic pathways for STRs, but also for other AGAs such as SPCs, KAS, and FORs and also the mixed type antibiotic HYG-A (see Section 2.2.4.3.1), starts with the formation of myo-inositol in a two-step pathway (Ca) that is not encoded in the itrAtt-clusters. The first step in streptidine biosynthesis (and any other myo-inositol utilising pathway) is the formation of a myo-inositol monophosphate (D-myo-inositol-3-phosphate or L-myo-inositol-1-phosphate) via L-myo-inositol-1-phosphate synthase, which in actinomycetes... 

SfrF04.2 NeoC 430 17039 2-Deoxy-icyZZo-inosose synthase (cyclase)... 

SteK17.24 TobC 386 17039 2-Deoxy-icy//o-inosose synthase (cyclas... 

Odakura et al. used a high producer derivative of M. olivasterospora MK-70 (DSM 43868), strain KYI 1250, to isolate 25 mutants blocked in at least 10 different steps of biosynthesis, as juged from complementation patterns in cosynthesis or biotransformation studies using vcy/to-inosose, cy/to-inosamine... 

Formation of the Initial Cyclitol. The first steps of FOR production are the same as in the biosynthesis of STR in short, the first step in FOR biosynthesis is postulated to be the formation of a myo-inositol monophosphate (D-myo-inositol-3-phosphate or L-myo-inositol-1-phosphate) via the cellular l-myo-inositol-1-phosphate synthase as in the STR pathway (Ca pathway see Section 2.2.1.2). As in the itr-Att-clusters, no gene for this enzyme has been found in the/or-cluster. As a second step in FOR biosynthesis the dephosphorylation of D-myo-inositol-3-phosphate via an inositolmonophosphate phosphatase has to follow. A putative gene product with this activity is that of the ForA protein (cf. Tables 2.17 and 2.18). The cyclitol is postulated to be first converted via two enzymes, a cluster-encoded myo-inositol 3-dehydrogenase (ForG member of the GFO/IDH/MocA oxidoreductase family) and the L-glutamine icy//o-3-inosose 3-aminotransferase (ketocyclitol aminotransferase I ForS), to icy//o-inosamine (3-deoxy-3-amino- cy/to-mositol). 

SteO08.22c AprC 384 17039 2-Deoxy-scyllo -inosose synthase,cyclase... 

Dextro-Inosit (36), laevo-Inosit (38), epi-Inosit (40) und neo-Inosit (42) bevorzugen eine Sesselform mit zwei axialen und vier aquatorialen Hydroxylgruppen. Bei alien vier Substanzen wird nur eine der beiden axialen Hydroxylgruppen in eine Ketogruppe hbergeftihrt. Die katalytische Oxydation von dextro-Inosit (36) gibt (- -)-dextro-Inosose-l (37), die Oxydation von laevo-Inosit (38) (—)-laevo-Inosose-l (39). Man... 

Hexa-0-(trimethylsilyl)-mj/o-inositol is a solid,112 and this compound and the crystalline per(trimethylsilyl) ethers of scyllo-inositol and myo-inosose-2 have been fully characterized by Loewus,407 who has proposed these compounds as suitable internal standards. The scyllo- and myo-inositols, together with myo-inosose-2, have also been used in a study on the use of electron-capture detectors with trimethylsilyl derivatives.579... 

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