Cyclitol epoxides

Access to new cyclitol thiirane derivatives has been reported by reaction of cyclitol epoxides with dimethylthioformamide in trifluoroacetic acid. For example the episulfide analogue 90 was produced from the conduritol B epoxide compound 91. Several similar examples were described starting from cyclitol epoxides prepared by known methods. 

Figure 13.8 Cyclitol epoxides and aziridine may feature ideal conformational behavior for retaining p-exoglucosidases inhibition.

Full details on new methods for the synthesis of A/-alkyl- and N,lV-dialkyl-derivatives of 2-amino-2-deoxy-D-glucose (cf. Vol.26, Ch.9, ref.36) have been reported. Four 1,4-imino-linked carbadisaccharides, e.g. 63, were synthesized by reaction of methyl 4-amino-4-deoxy-a-D-glucoside with a cyclitol epimine. The 1,6-linked di-mnnno-analogue 64 was obtained similarly by reaction of methyl 6-amino-6-deoxy-a-D-glucoside with a cyclitol epoxide, and was found to be an inhibitor of Jack bean a-D-mannosidase. ... 

A compound containing a sulfonyloxy group adjacent and frans-situated to a free hydroxyl group is converted to an epoxide by the action of bases.85 The application to cyclitols of this well-known reaction will be discussed in Section III, 2 (see p. 181). 

Because of the large number of different nucleophiles that can be used, the opening of epoxides is a powerful means of gaining access to a vast variety of highly functionalized cyclitols. It also seems to be a valuable method for production of carbasugars and aminocarbasugars, by use of appropriate nucleophiles. For gen-... 

Reviews on sugar epoxides and on epoxide reactions have appeared. Cyclitols containing both an epoxide group and a double bond, such as (118), have been prepared from benzene glycol diacetate. These products react with ammonia to give conduramines (119, Ac = H) which can be converted into inosamines or inosadiamines, such as (121). ... 

Epoxidation of the adduct (125) affords a cyclitol (126) containing both a 1,2-anhydro and a 1,4-anhydro ring, as well as a carbonate ester ring. By acidic and basic hydrolysis of (126), a total synthesis of myo- and aZlo-inositol was achieved, although not, as claimed, the first total synthesis... in this series. As noted above, these inositols were also obtained by hydrolysis of (124). ... 

The trithiocarbonates may prove useful as intermediates for the synthesis of sugar dithiols from epoxides. Ring opening by reductive cleavage with lithium aluminum hydride gives excellent results with aliphatic and ahcyclic trithiocarbonates. When both carbon atoms are secondary, the product is a iraws-dithiol for example, cyclohexene oxide, which is converted into a irans-trithiocarbonate, gives, on reduction, cyclo-hexane-1,2-dithiol. The reaction has been used in the cyclitol series for the preparation of 1,2-dithio-neo-inositol and 1,2-dithio-ir-inositol, from 1,2-anhydro-alZo-inositol. The inositol trithiocarbonates show pronounced Cotton effects in their optical rotatory-dispersion spectra. 

Other carba disaccharides to have been prepared include carba-a-o-Glcp-, carba-a-D-Manp-, carba-P-D-Man/j- and carba-P-o-GIcNAcp- (l- 4)-l,6-anhydro-2,3-0-isopropylidene-P-D-mannopyranoses. The a-linked compounds were prepared by adding the anion of l,6-anhydro-2,3-C>-isopropylidene-p-D-mannopyranose to epoxide 98 and the P-linked derivatives were obtained from the a-linked compounds by epimerization after oxidation of the free cyclitol OH group. Further standard transformations of the free cyclitol OH also gave the cyclitol configurations noted above.In a similar way, opening of a cyclitol... 

The cyclitol doived glycoconjugate analogue 122 has been prepared by Lewis add promoted coupling of alcohol 123 with epoxide 112 followed by dil droxylation and removal of the protecting... 

A total synthesis of the natural product cyclophellitol, 38, a P-glucosidase inhibitor, has been described starting from >-glucose, in which the key transformations are Fenier rearrangement of 35 and a stereoselective epoxidation of 37 (Scheme 10). The natural product (-)-ovalicine 39, another epoxy cyclohexane, has been prepared from the cyclitol L-quebrachitol (Scheme 11). ... 

Treatment of the epoxide 98 with TMSCN led unexpectedly to compound 99. Epoxidation of cyclopentadiene yields a di-epoxide which on treatment with sodium azide gives a mixture of products from which cyclitol 100 can be obtained as a useful precursor to carbocyclic nucleosides and amino cyclitols. 

Various cyclitols (and acyclic polyols) have been desynunetrized by formation of dispoke intermediates. (See for example, Vol. 28, p. 237, ref. 115). L-Chiro-inositol can be converted to the silyl derivative 67 in which the trans-diol units are protected on reaction with l,3-dichloro-l,l,3,3-tetraisopropylidisiloxane (TipsQ). Compound 67 was further converted into conduritol B epoxide and its thioepoxide analogue. The conversion of some tetra-O-substituted myo-inosi-tols into adipic dialdehyde derivatives is mentioned in Chapter IS. 

The microbial oxidation of benzene and its derivatives using Pseudomonas putida have been used in several cyclitol syntheses. These include the preparation of conduritol D and the deuterated compound 99", D-cA/ro-inositol and D-cAiro-3-inosose for which the key step involves a one pot oxidation-protection to an epoxy-acetonide derivative," " and racemic quebrachitol." Also reported are the syntheses of (+)-D-chrro-inositol, a//o-inositol, muco-inositol and neo-inositol from a halogenated conduritol epoxide." ... 

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