Altropyranoside, methyl 2,6-anhydro

Altritol, tetra O-acetyl-1,5-anhydro-3-de-oxy-3-C-(hydroxymethyl)-D-, 98 Altropyranoside, methyl 4-0-benzoyl-6-bromo-2,6-dideoxy-2-(p-tolylsulfona-mido)-3-0-p-tolylsulfonyl-a-D-, 267 —, methyl 4,6-O-benzylidene-a-D-, 107 2,3-dinitrate, denitration of, 266 —, methyl 4,6-0-benzylidene-2-0-(meth-ylsulfonyl)-a-D-, 3-nitrate, infrared spectrum, 256... 

Alloslde, methyl 2-acetamido-2-deoxy-a-D-, derivatives, 202 —, methyl 2,3-anhydro-4,6-0-benzyli-dene-a-D-, 51, 227 Altraric acid, 2,5-anhydro-n-, 55 Altronic acid, 2-amino-2-deoxy-n-, 54 —, 2,5-anhydro-D-, 55 Altropyranoside, methyl 3-amino-3-deoxy- 8-D-, 50 Altrose, oxidation of, 15 —, 2-amino-2-deoxy-D-, methyl ethers of, 202, 214... 

Methyl 2,6-anhydro-a-D-altropyranoside-2 5B g l,4-Anhydro-ot-D-allopyranose-Bi,4 9 1,2-0-Ethylidene-a-D-glucopyranose- S3 10 p-L-Altropyranose-2So... 

Based on the fact that methyl 2,3-anhydro-a-D-mannopyranoside (II) is hydrolyzed17 by sodium methoxide to give, on subsequent methyla-tion, a mixture of two methyl trimethyl hexosides (methyl 3,4,6-trimethyl-a-D-altropyranoside and methyl 2,4,6-trimethyl-a-D-glucopyranoside) it was anticipated that the action of ammonia on II would follow essentially the same course. This was found to be the case, for with ammonia II yielded compounds which were converted to methyl 4,6-dimethyI-3-aeetamido-a-altropyranoside (III) and methyl 4,6-dimethyl-2-acetamido-a-D-glucopyranoside (IV) (10% yield). 

A novel method of opening of oxiranes involves the use of (chlo-romethylene)dimethyliminium chloride (39) [see Section II,2c p. 250], monochlorodeoxy or dichlorodideoxy derivatives are obtained, depending upon the reaction conditions employed.83 Thus, methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (110) reacts with 39 in 1,1,2,2-tetrachloroethane at room temperature to give, upon hydrolysis of the primary adduct 111 with an aqueous solution of sodium hydrogen carbonate, methyl 4,6-0-benzylidene-2-chloro-2-deoxy-3-0-formyl-a-D-altropyranoside (112). If a solution of 39 and 110 in 1,1,2,2-tetrachloroethane is heated at reflux temperature, methyl 3,4-0-benzylidene-2,6-dichloro-2,6-dideoxy-o -D-altropyrano-side (113) is obtained in high yield the n.m.r. spectrum of 113, like that of 47 (see Section II, 2c p. 250), showed the presence of two diastereoisomers which differed in the configuration of the benzyl-idene-acetal carbon atom. 

Neighboring-group participation by the vicinal, trans-acetoxyl group (see p. 125) serves to explain the abnormal behavior of methyl 4-0-acetyl-2,3-anhydro-6-0-benzyl- or -trityl-a-D-gulopyranoside with hydrogen chloride in acetone, or with 80% aqueous acetic acid, which give D-galactose, instead of the D-idose, derivatives.67 In the same way, 2-0-acetyl-3,4-anhydro-D-altropyranosides yield D-man-nosides, not D-idosides.9 6z(see p. 125). 

As might be expected, the nitrous acid deamination of methyl 2-amino-4,6-0-benzylidene-2-deoxy-a-D-altropyranoside (10) hydrochloride leads45,46 uniquely to methyl 2,3-anhydro-4,6-0-benzylidene-a-D-allopyranoside (11). The benzylidene group does not play an... 

The deamination of methyl 3-amino-3-deoxy-/3-D-altropyranoside was studied in 1934, but the products were not fully characterized.14411 The syrupy product was converted into a methylated derivative that had an elemental analysis corresponding to that calculated for a methyl tetramethylhexoside. The conditions used for methyl-ation would have opened an epoxide ring. Methyl 2,3-anhydro-4,6-0-benzylidene-a-D-mannopyranoside precipitated quantitatively from solution when the corresponding 3-amino-3-deoxyaltroside derivative was deaminated in aqueous medium.145 Epoxide formation was likewise reported to be quantitative in the deamination of the analogous 2-amino-2-deoxyaltroside.83 145 On deamination, 4-amino-l,6-anhydro-4-deoxy-/3-D-mannopyranose also gave an epoxide, namely, 1,6 2,3-dianhydro-/3-D-talopyranose, in unspecified yield.146... 

Methyl 4,6-O-benzyIidene-a-D-aItropyranoside. Triturate 4.0 g (0.015 mol) of the foregoing anhydro derivative in a mortar with a solution of 5 g of potassium hydroxide dissolved in 140 ml of water. Transfer the suspension to a round-bottomed flask and heat the mixture under reflux until all the solid has dissolved (about 28 hours). During this period solid material tends to creep up the inside of the flask surface shake periodically to re-suspend material. Remove the trace of insoluble matter which remains and neutralise the cooled filtrate with carbon dioxide (use phenophthalein as an indicator). Extract the solution with five 25 ml portions of dichloromethane, wash the combined extracts with a little cold water, dry over anhydrous sodium sulphate and remove the solvent under reduced pressure (rotary evaporator). Crystallise the syrup by scratching a small portion on a watch glass with ether stir the bulk syrup with ether and the seed crystals. Filter off and recrystallise the product from a small quantity of methanol to obtain 3.5 g (83%) of methyl 4,6-0-benzylidene-oc-D-altropyranoside, m.p. 174 °C, [a]D°+115° (c2 in CHCI3). 

In the pyranose ring, the true cis orientation is encountered in boat forms (for example, XIX) or in the half-chair forms (for example, XX) and again, as illustrated by the very rapid uptake of lead tetraacetate by methyl 2,6-anhydro-a-D-altropyranoside,84 which is known to have a boat conformation,... 

Treatment of an epoxide, namely methyl 2,3-anhydro-4,6-0-benzylidene-oi-D-allopyranoside (78, Scheme 21), with nitryl iodide using methanol as the solvent has been reported.123 Rather than the expected nitration, opening of the epoxide occurred to afford 30% of methyl 4,6-0-benzylidene-3-0-methyl-oi-D-glucopyranoside (79), 10% of methyl 4,6-0-benzylidene-2-0-methyl-a-D-altropyranoside (80), and a water-soluble material. The water-soluble material was later determined to be a mixture of the 2-0- (81) and 3-0-methyl (82) products, with the benzylidene acetal removed, a result consistent with a later study.124 Performing the reaction in the absence of the silver salt resulted solely in formation of the water-soluble product. The preponderance of the diequatorial product 81 is in violation of the Flirst-Plattner rule, which predicts more of the diaxial product. The authors explanation for the anti-Fiirst-Plattner addition is as follows. 

The only optically active pyranoeide known to possess the 0° angle is methyl 2,6-anhydro-a-D-altropyranoside. This substance exhibited a very high conductance effect and a low rotational shift (see reference 11). 

In the limited number of examples where the trans- 1,2-diols would be diaxial if the compound adopted a chair conformation, mixtures are also usually obtained. To form dibutylstannylene acetals, conformational changes to skew, boat, or alternative chair conformations are required. Conversion to the boat is easy for l,6-anhydro-/3-D-glucopyranose149 and methyl a-D-idopyranoside, but may be more difficult for methyl 4,6-0-benzylidene-a-D-altropyranoside. 

Methyl 4,6-0-benzylidene-a- and jS-n-altropyranosides have been prepared from the corresponding n-glucosides, which were first converted into the 2,3-di-p-toluenesulfonates. Subsequent treatment of the p-toluenesulfonate with sodium methoxide in the cold afforded the 2,3-anhydro derivative. The latter was then converted into the n-altroside by means of boiling potassium hydroxide, Methyl 4,6-0-benzylidene-a-D-altropyranoside is very resistant to oxidation by periodate ion and does not form a cuprammonium complex — in accordance with the expected CA conformation (34). 

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