Mannofuranose

Fig. 3.—A. Initial Slope Approximation to Determine the Initial, Nonselective, Spin-Lattice Relaxation Rate of H-S of 2,3 S,6-Di-0-isopropylidene-a-D-mannofuranose (2) in Me2SO-d Solution. (Points between 0.01 and l.SS s were selected for tracing the best straight line.) B. The Same as in A for H-1 of a Partially Deuterated Sample of 1,6-Anhydro- -cellobiose Hexaacetate (3). [Note that the relaxation of H-1 is strongly dependent on the choice of I value. An R (ns) value of 0.24s was obtained from the data points 0 t 5s, where a value of 0.18 s was obtained from the terminal decay 5 lOs (see text).]...

C6H1206 Ca2+ Cl2 4 H20 yS-D-Mannofuranose calcium chloride, tetrahydrate MANCAC 30 465... 

For 2,3 5,6-di-O-isopropylidene-a-D-mannofuranose (183), separation of the anomeric products (184 and 185) was possible,135 and their structures were elucidated by periodate-oxidation studies. The configurational assignment for these products was based on the greater value of the specific rotation for the a anomer, as compared with that of the j3 anomer. The higher chromatographic mobility of one of the... 

Szarek et al. were the first to develop this mode of glycosylation, which was demonstrated for ribonudeoside synthesis. In the reaction, a protected mannofuranose... 

Similarly, starting from 2,3 5,6-di-0-isopropylidene-D-mannofuranose 72, a one-pot procedure that implies the synthesis of glycosyl sulfones by Horner-Wadsworth-Emmons olefination with phosphonate 73, followed by subsequent Michael addition and Ramberg-Backlund reaction92 gives compound 74 in 78% yield93 (Scheme 24). 

Carbohydrate lactones have been used as the carbonyl reagent in the Reformatsky reaction. Thus, 2,3 5,6-di-O-cyclohexylidene-D-mannono-1,4-lactone [44, obtained by oxidation of the mannofuranose derivative (49)] reacted with ethyl bromoacetate and zinc to give the protected 2-deoxy-3-octulosonic acid ethyl ester (45a) in 69% yield (50). Ketonic hydrolysis with potassium hydroxide in aqueous methanol, followed by acidification and heating, afforded the 1-deoxyheptulose derivative 45b. Similarly, starting from compound 44, the 1-C-substituted allyl and propar-gyl lactols were prepared on reaction with allyl or propaigyl bromides in the presence of zinc (51). 

Optically active dihydrooxazines 230 are produced by the reaction of the chiral a-chloronitroso compound 228 derived from D-mannofuranose with a variety of 1,3-dienes in the presence of ethanol at low temperatures via the primary adducts 229 (equation 122). Penta-1,3-diene, for instance, yields a mixture of the regioisomers 231 and 232113. 

Vinyl glycosides are difficult to prepare by conventional vinylation procedures although it has been reported that 2,3 5,6-di-0-isopropyl-idene-D-mannofuranose with acetylene in the presence of potassium hydroxide afforded vinyl mannosides A much better transvinylation procedure was used by Fletcher and coworkers as shown in Scheme 12 to give mixed products which, after chromatographic separation, were converted to vinyl a- and p-D-glucopyranosides by treatment with sodium in liquid ammonia... 

A Mn(III,IV) dinuclear complex supported by the aldohexose o-mannose (o-Man), BaJMn2-(b-D-Mari/T[ 5)2]Cl (58) (where Man/ = mannofuranose), was reported by Geisselmann et al. This... 

Measurements of the influence of boric acid on the rotation and conductivity of 8-D-mannose yielded the results shown in Table VII. For /3-D-mannose both the rotation and the increase in conductivity become greater and these phenomena run practically parallel. Thus, it is not surprising that we assumed at the time that /3-D-mannose should be allotted the frans-mannofuranose configuration, and its isomer, which... 

As a matter of fact the high value of A in the equilibrium solution (344.4) is a sign that a very large proportion of D-mannofuranoses is present in this connection it must be borne in mind that the cis as well as the trans modification has in this case two favorably situated adjacent hydroxyl groups attached to carbon atoms 2 and 3. Since a-(trans)-T>-mannose has not been examined, no further conclusions can be drawn. 

Finally, I would draw attention to the reaction of n-mannose with acetone the 2,3 5,6-diisopropylidene-n-mannofuranose is very readily formed. 

The strategy for the synthesis of carba-hexofuranoses and -pentofuranoses is summarized in Scheme 16. Five new carbaanalogues of hexofuranoses were synthesized 74, 73 and the enantiomer a-L-mannofuranose, and the a-L and /3-D-glucofuranoses. The carba-analogues of the 5-deoxyhexofuranoses with a-L- and -D-lyxo-, and a-L-xyZo-configurations, which we have also prepared [98b], have recently been described, either with the same configuration, or as the enantiomeric compound, or as a racemic mixture [86]. Several of the hitherto known compounds were now obtained in a crystalline state... 

Two reports on the preparation of polyhydroxylated [13]thiazolo[3,2a]azepane derivatives have been published. The one reports the synthesis of the p-tum mimetic 22 from D-glucurono-3,6-lactone and L-cysteine <99TL477>, whilst the other describes, for example the preparation of 23 in 78% yield from 6-0-tosyl-23-0 isopropylidene-D-mannofuranose and 2-aminothioethanol <99S839>. 

HaC-C-NOz 1 ch3 Na2S, DMF, bv ch3 2,3 5,6-Di-0-isopro- pyliden-l-desoxy-1- isopropyliden- mannofuranose 96 2... 

In a number of reactions on furanose derivatives, steric restraints interfere with anhydro-ring formation. 6-Deoxy-2,3-0-isopropylidene-5-O-tosyl-L-mannofuranose is readily converted by sodium methoxide into methyl 6-deoxy-2,3-0-isopropylidene-/3-D-allofuranoside. In this... 

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