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An alternative synthesis of the key intermediate 8 for the synthesis of wybutine 1 has been attained through the Heck reaction between (S)-N-(methoxycarbonyl)vinylglycine 13 and 1-benzyl-7-iodowye 7. The nucleoside version of this method using 7-iodo-3-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)wye 19, followed by catalytic hydrogenation, afforded a mixture of diastereoisomers 22 and 23. Separation of isomer 22 by means of high-performance liquid chromatography, followed successively by esterification and deprotection has accomplished the first synthesis of 3-(β-D-ribofuranosyl)wybutine 3, which is the most probable structure for wybutosine isolated from phenylalanine transfer ribonucleic acids.

(R)-[2-Carboxy-2-[(methoxycarbonyl)amino]ethyl]triphenylphosphonium chloride (1) was converted by treatment with anion exchange resin (HCO-3) into the inner salt 13h, which gave a better yield (43%) than 1 in the Wittig reaction with benzaldehyde to afford the [S-(E)]-(2-phenylvinyl)glycine derivative 24. The inner salt 13i bearing an N-benzyloxycarbonyl group was prepared by hydrogenolysis of (R)-[3-benzyloxy-2-[(benzyloxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11e) over palladium on carbon, followed by dehydrochlorination. Hydrogenolysis of 11e over Pearlman's catalyst afforded the unprotected phosphonium chloride 12 (X=Cl). N-tert-Butoxycarbonylation of 12 followed by dehydrochlorination afforded 13j, which was more efficiently prepared through hydrogenolysis of (R)-[3-benzyloxy-2-[(tert-butoxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11f).The usefulness of 13h-j as building blocks for the synthesis of configurationally labile (2-arylvinyl)glycine derivatives was exemplified by the Wittig reactions with piperonal, which exclusively afforded the (E)-isomers 18h-j with high optical purity in 28-39% yield.

(R)-[2-Carboxy-2-[(methoxycarbonyl)amino]ethyl]triphenylphosphonium chloride (1) was converted by treatment with anion exchange resin (HCO-3) into the inner salt 13h, which gave a better yield (43%) than 1 in the Wittig reaction with benzaldehyde to afford the [S-(E)]-(2-phenylvinyl)glycine derivative 24. The inner salt 13i bearing an N-benzyloxycarbonyl group was prepared by hydrogenolysis of (R)-[3-benzyloxy-2-[(benzyloxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11e) over palladium on carbon, followed by dehydrochlorination. Hydrogenolysis of 11e over Pearlman's catalyst afforded the unprotected phosphonium chloride 12 (X=Cl). N-tert-Butoxycarbonylation of 12 followed by dehydrochlorination afforded 13j, which was more efficiently prepared through hydrogenolysis of (R)-[3-benzyloxy-2-[(tert-butoxycarbonyl)amino]-3-oxopropyl]triphenylphosphonium chloride (11f).The usefulness of 13h-j as building blocks for the synthesis of configurationally labile (2-arylvinyl)glycine derivatives was exemplified by the Wittig reactions with piperonal, which exclusively afforded the (E)-isomers 18h-j with high optical purity in 28-39% yield.

Vinylglycine (2) has been shown to undergo racemization under acidic conditions. Optically pure 2 was obtained from 2.HCl by enzymatic hydrolysis through N-acetylvinylglycine (5), followed by recrystallization. (S)-N-(Methoxycarbonyl)vinylglycine (6) was configurationally so unstable under acidic conditions that 6 could not be obtained from 2 in an optically pure form. On the other hand, configurationally stable (S)-N-(9-phenylfluoren-9-yl)vinylglycine methyl ester (9) was synthesized from (S)-homoserine; 9 was hydrolyzed with sodium hydroxide to afford the carboxylic acid 10 of more than 99% ee.

The Vilsmeier-Haack reaction of 3-(2, 3, 5-tri-O-acetyl-β-D-ribofuranosyl)wye (7c) followed successively by reduction with sodium borohydride and catalytic hydrogenolysis afforded the 7-methyl derivative 12c, which provided the title compound 12a on deprotection. Compound 12c was more effectively produced by direct hydrogenolysis of the 7-formyl derivative 8c, especially by use of Pearlman's catalyst. Similar treatment of 1-benzyl-7-formylwye (14) led to a better synthesis of 7-methylwye (1b), the fluorescent base isolated from Archabacterial transfer ribonucleic acids. Although hydrogenolysis of the 6-formyl compound 11 took place smoothly even over ordinary palladium on charcoal to afford 12c, this route had a bottleneck in the step of transformation of 8c into 11.Compound 12a proved to be highly sensitive to acidic hydrolysis at the glycosyl bond and the rate determined in 0.1N hydrochloric acid at 25°Cwas virtually the same as that of 3-β-D-ribofuranosylwye (7a).