L-lyxose derivatives

The L-lyxose derivative was prepared from the anti-adduct 13a of 3-phenylpropanal as outlined below, and the absolute configuration was determined by comparison with the optical rotation of an authentic sample(lO) derived from D-lyxose. 

C-Glycosides. Thiophenyl glycosides undergo ready free-radical allylation with allyl- or methallyltri- -butyltin. Thus the L-lyxose derivative 1 reacts with allyltri-/ -butyltin under photochemical initiation to give 2 and 3 in the ratio 90 10. The reaction... 

Good diastereoselectivities were observed for the hetero Diels-Alder addition of homochiral 1,3-dienes with achiral acyl-nitroso dienophiles. An example is shown in Scheme 13.85 for the total synthesis of 4-amino-4,5-dideoxy-L-lyxose derivatives 300 and 301, potent inhibitors of a-L-fucosidase [160]. 

SCHEME 13.85 Defoin s syntheses of 4-amino-4,5-dideoxy-L-lyxose derivatives. 

Starting with methyl 3-acetamido-3-deoxy-2,4-di-0-(methylsulfonyl)-/3-L-xylopyranoside (96), Baker and Schaub" > > were able to obtain the D-ribose derivative (98) after prolonged refluxing. When the solvolysis of (96) was conducted in refluxing 95% ethanol, an intermediate was formed which was assumed to be the L-lyxose derivative (97) this could be converted into (98) by further reaction with sodium acetate in 2-methoxy-... 

The first example of methoxyl participation reported in carbohydrate chemistry was the migration454 of a methoxyl group from C-l to C-4 during an attempted benzoate displacement reaction with 2,3,5-tri-O-benzyl-4-O-p-tolylsulfonyl-D-ribose dimethyl acetal (185). Instead of the 4-O-benzoyl-L-lyxose derivative expected, the isomeric l-0-benzoyl-2,3,5-tri-0-benzyl-4-0-methyl-L-lyxose methyl hemi-acetal (187) was obtained, presumably by way of the cyclic, oxonium ion 186. Solvolysis of the related aldehydo sugar, namely, 2,3,5-tri-O-benzyl-4-O-p-tolylsulfonyl-D-ribose, readily gives 2,3,5-tri-O-benzyl-L-lyxofuranose, and the reaction probably involves participation by the free aldehyde group.455... 

Participation by the acetal function is common in displacement reactions of carbohydrate derivatives. An example of participation by an acetal group in an open-chain carbohydrate has been provided by Hughes and Speakman. Treatment of ribose derivative (152) with tetrabutyl-ammonium benzoate in 1-methylpyrrolidone gave 2,3,5-tri-0-benzyl-4-0-methyl-L-lyxose methyl hemiacetal 1-benzoate (154) instead of the expected 4-O-benzoyl-L-lyxose derivative. The oxonium ion (153) was thought to be an intermediate. 

Reactions.—1,3-Dithianyl Anions. 1,3-Dithianyl anions continue to find wide-ranging utility in the synthesis of diverse structures, including 2-deoxy-L-lyxose derivatives, eburnamine precursors, " l,2-diformyl-6,6-dimethylcyclohex-2-en-l-ol, cannabinoids, tertiary acyloins, cyclitols, unsaturated carboxylic acids, the terpenes egomaketone and a- and jff-curcumene, (205)-20-hydroxycholesterol, norpyrenophorin, pyrenophorin, and vermiculine, compounds with chiral methyl groups, " (+)-rrans-burseran, enones, " the macrocyclic lactam A-methylmaysenine, olivin, macrocyclic acetylacetone crown ethers, [5.1]metacyclophane, ( )-laurencin, monosaccharides, y-keto-esters and their precursors, muscarine analogues, quinols, epi-... 

The total synthesis of pseudomonic acids has been reviewed, and Keck has streamlined his earlier synthesis (Vol. 18, p.247 Vol. 19. p.257) of pseudomonic acid C by direct linkage of an L-lyxose derivative with a chiral side-chain, using free-radical methods. ... 

The synthesis of alkene (32) in four steps from D-glucose has been achieved and attempts at synthesizing cyclic alkenes from L-rhamnose and L-lyxose derivatives are... 

Streptose is the first branched-chain sugar to have been identified as a component of a biological compound produced by a microorganism. This dicarbonyl sugar is known only in its derivatives. The chemistry of streptose and streptomycin has been lucidly reviewed by Lemieux and Wolfrom.1 In this article, it was noted that streptose must be either 5-deoxy-3-C -formyl-L-ribose or 5-deoxy-3-C-formyl-L-lyxose. Since then, the presence of the latter configuration (XXXIV) has been definitely established by Wolfrom and DeWalt,66 who found that N-acetyltetrahydrostreptobi-... 

In the pentose series, attack has also been observed to occur mainly from the less-hindered side of the double bond, as in the addition of trifluoro(fluoroxy)methane to di-O-acetyl-D-arabinal. Trifluoromethyl 3,4-di-0-acetyl-2-deoxy-2-fluoro-/3-D-arabinopyranoside and 3,4-di-0-acetyl-2-deoxy-2-fluoro-/J-D-arabinopyranosyl fluoride were obtained,72,74 together with a very small proportion of 3,4-di-0-acetyl-2-deoxy-2-fluoro-a-D-ribopyranosyl fluoride.74 With di-O-acetyl-D-xylal, however, the lyxose derivatives were mainly obtained.72,73 The suggestion has been made73 that the greater conformational mobility of pentopyranoses results in a preponderance of the C d) conformer of the D-lyxose derivatives,72,73 such that F-l and CFsO-l are axially disposed. For further reactions of unsaturated carbohydrates with tri-fluoro(fluoroxy)methane, see Section 11,9. 

There are two lectins of distinct, sugar-binding specificity in Ulex extracts.196,225 Using ethanol fractionation, Flory225 initially discriminated between Ulex I, which is readily inhibited by L-fucose derivatives, and Ulex II, which binds /3-D-glucosides. (A comprehensive discussion of Ulex II purification and properties is presented in Section III,5.) Flory s 50-70% ethanol precipitate enriched in Ulex I, was slightly inhibited by D-arabinose, D-ribose, and D-lyxose, in addition to L-fucose.225 This preparation agglutinated human, epithelial, cheek-cells of secretory individuals only.225... 

R, = OH, Rj = H, R2 = OH, R4 = CHjOH in Table 3), the enantiomeric compound of the one just reported could be easily prepared. Aldol condensation products were obtained as diastereomeric mixtures from L-sugars, such as L-fucose, L-xylose, L-lyxose, and o-sugars epimeric to o-mannose relative to the 3-position, such as D-allose and o-gulose [46-48]. Table 4 lists the corresponding aldol condensation products isolated as diastereomeric mixtures. Also, 3-deoxy-D-mannose by condensation with pyruvate gave a diastereomeric mixture of 6-deoxy-KDN furanose derivatives [43]. All these results confirm that sialic acid aldolase, similar to other aldolases, exhibits broad specificity toward the electrophilic acceptor on the other hand, only pyruvate was reported acceptable as the donor [10]. But very recently, in contradiction to that, 3-fluoro-Neu5Ac and 3-fluoro-KDN could be prepared by the sialic acid aldolase-catalyzed condensation of 3-fluoropyruvate and Af-acetylmannosamine or o-mannose (Scheme 5) [47]. 

Walker et al. have described by tliis method a seven-step synthesis of 4-thio-2-deox-y-i3-eri f/7ro-pentosc (37) from 2-dcoxy-D-erir/ira-pentosc via dithioacetals 35 and 36, involving inversion at C-4 by Mitsunobu reaction and final cyclization of the dithioacetal, accompanied by further inversion at C-4. Secrist et al.- have synthesized 39 from the ribose derivative 38 using the same method. Similarly, Imbach et al. have prepared 1,4-dithio-D-ribofuranosides 39 from L-lyxose and from D-ribose,and 1,4-dithio-L-lyxofuranosides 40 from D-ribose. Mackenzie... 

Synthesis of Amino Sugars by Reduction of Hydrazine Derivatives. 2-Amino-2-deoxy-L-lyxose (L-Lyxosamine) Hydrochloride, D. Horton, M. L. Wolfrom, and A. Thompson,/. Org. Chem., 26, 5069-5074 (1961). 

Defoin et al. has developed the synthesis of hydroxy-ethane derivative 148, a nanomolar a-L-fucosidase inhibitor, starting from chiral nitrone 145, an analog of 5-deoxy-L-lyxose that was derived from o-ribose [67]. Nitrone 145 reacted easily in C2CI4 at 50 °C with phenyl vinyl ether to give cycloadducts 146a and 146b quantitatively in a 85 15 ratio (Fig. 34). The major isomer 146a was converted via pyrrolidine 147 to the C-a-L-fucoside 148 in four steps in an overall yield of 59%. 

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