Kyoichi A. Watanabe

Nucleosides—LXVIII: Synthetic studies on nucleoside antibiotics. 5. 4-amino-2,3-unsaturated sugars related to the carbohydrate moiety of blasticidin S

Abstract Methyl 4-amino-2,3,4-trideoxy-α- d -erythro-hex-2-enopyranoside (24) and its crystalline dibenzoate (26) were synthesized from methyl 4-azido-4-deoxy-6-O-trityl-α- d -glucoside (1) by a route involving the 2,3-anhydromannoside derivative (18) and the 3-iodo-altroside (20). Treatment of 20 with mesyl chloride in pyridine gave the 2-enopyranoside (22) which after reduction with sodium dithionite followed by debenzoylation afforded the 2,3-unsaturated-4-amino sugar derivative (24), a member of a new class of carbohydrates. An alternate synthesis of the key intermediate (22) from methyl 4-azido-4-deoxy -2,3-di-O-mesyl-6-O-trityl-α- d -glucoside (2) was achieved via the allo-epoxide (12). The synthesis of methyl 4-amino-2,3,4-trideoxy-α- d -erythro-hex-2-enopyranosiduronic acid (38), related to the carbohydrate moiety of Blasticidin S, was achieved from 18 by oxidation and esterification to the 2,3-anhydro-4-azido-α- d -mannosiduronate (33) which was converted into the 3-iodo-altrosiduroate (35) and thence to methyl (methyl 4-azido-2,3,4-trideoxy-α- d -erythro-hex-2-enosid)uronate (6). Reduction and saponification of 6 afforded crystalline 38. An improved synthesis of 6 was achieved from 12 via the crystalline 2,3-allo-epoxides 44 and 45. Conformational aspects of these 4-amino-2,3-unsaturated sugars are discussed.

Nucleosides: Part LXII. Synthetic studies on nucleoside antibiotics. 2.syntheses of methyl 4-amino-4-deoxy-d-glucosiduronic acid derivatives related to the carbohydrate moiety of gougerotin☆

Abstract The first synthesis of 4-amino-4-deoxy- d -hexuronic acid has been achieved. Tritylation of methyl 4-azido-4-deoxy-α- d -glucopyranoside ( 1 ) gave the 6-trityl ether ( 2 ) which was converted into its 2,3-dibenzoate ( 3 ) and deritylated to methyl 4-azido-2,3-di- O -benzoyl-α- d -glucopyranoside ( 5 ). Oxidation of 5 afforded the glucuronic acid derivative 6 which upon esterification to 7 , followed by reduction and benzoylation yielded methyl (methyl 4-benzamido-2,3-di- O -benzoyl-4-deoxy-α- d -glucopyranosid)uronate ( 8 ), the structure and conformation of which were firmly established by n.m.r. analysis. De-benzoylation of methyl (methyl 4-azido-2,3-di- O -benzoyl-4-deoxy-α- d -glucopyranosid)uronate ( 7 ) with sodium methylate to 9 , followed by de-esterification and subsequent hydrogenation afforded crystalline methyl 4-amino-4-deoxy-α- d -glucopyranosiduronic acid ( 11 ), the structure of which was established by esterification and benzoylation to 8 . N -Acetylation of 11 yielded methyl 4-acetamido-4-deoxy-α- d -glucopyranosiduronic acid ( 14 ) which was esterified and peracetylated to the methyl ester 16 . Derivative 16 was also obtained by hydrogenation and peracetylation of 9 . Epimerization at C-5 was not observed in the conversion of 7 → 11, which suggests that a total synthesis of the gougerotin-derived C-substance from the 4-amino-4-deoxy-hexuronic acid derivatives reported herein is feasible.

Synthesis and Some Properties of Modified Oligonucleotides. II. Oligonucleotides Containing 2′-Deoxy-2′-fluoro-β-D-arabinofuranosyl Pyrimidine Nucleosides

Abstract In order to find the effects of unnatural nucleosides on the stability of duplex, several oligonucleotides containing 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-uracil(FAU),-cytosine (FAC) and -thymine (FMAU) were synthesized by two alternative approaches: phosphoramidite method on an ABI 392 synthesizer and H-phosphonate procedure on our GeneSyn I universal module synthesizer. It was shown from the melting profiles that the presence of FMAU has a large stabilizing effect on the duplex. Replacement of thymidine with FAU, or deoxycytidine with FAC resulted in the formation of less stable duplexes. Temperature-dependent CD spectroscopy demonstrated that the structures of the fluorine containing oligomers are very similar to those of unmodified oligomers.

The Chemistry of C-Nucleosides

A group of nucleosides in which the ribofuranosyl moiety is linked to a heterocyclic base through a carbon-to-carbon bond (hence called C-nucleosides) have been found in nature.(1) The first example was pseudouridine (ψ-uridine), which was isolated in 1957(2) as the fifth nucleoside obtained from “soluble RNA,” and its structure was established in 1962 as 5-(β-d-ribofuranosyl)uracil(3,4) (Fig. 1). It is now known that ψ-uridine is present ubiquitously in active transfer RNA (tRNA),(5) and that certain tRNAs deficient in ψ-uridine are incapable of participating in protein synthesis. (5, 6) This C-nucleoside is formed enzymatically from uridine after assembly of the tRNA chain. (7–10)

Synthesis of 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)hypoxanthine. The first direct introduction of a 2'-β-fluoro substituent in preformed purine nucleosides. Studies directed toward the synthesis of 2'-deoxy-2'-substituted arabinonucleosides. 8

Abstract The 3′, 5′-di-O-acetyl-, 3′-, 5′-di-O-balzyl-, 3′-O-acety -5-O-trityl- and 3′-, 5′ -di-O-trityl-2′-O-triflyl-1-benzylhnosine (8c, 15, 20C, and 27, respectively) were prepared and subjected to nucleophilic reaction with TASF. Thus, 3′, 5′-O-(1, 1, 3, 3-tetraisopropyldisiloxanyl)-1-benzylinosine (5c) was triflylated, desilylated, and then acetylated to give 8c. Also, 5c was converted into the 2′-O-tetrahydropyrnyl (W) derivative 11 which was desilylated and then benzylated to give 2′-O-tetrahydropyranyl-O3′, O5′, N1-tribenzylinosine (13). Removal of the THP group from 13 followed by triflylation afforded 2′-O-triflyld-O3′,O5′ N1-tribenzylinosine (15). 3′-O-Acetyl-2′ -O-triflyl-,O5′,N1-inosine (20) was prepared frmn 5′ -O-trityl-1-benzylhh (18c) by conversion into the 2′-, 3′-O-(di-n-butylstannylene) derivative which was treated with triflyl chloride and then acetylated. Treatment of 1-benzyl-inosine (4c) with trityl chloride in pyridine containing p-dimethylamino-pyridine afforded a mixture of 2′-,...

Nucleosides. CXIX. Substrate specificity and mechanism of action of cytidine deaminases of monkey plasma and mouse kidney

Abstract Cytidine deaminase (cytidine aminohydrolase, EC 3.5.4.5), partially purified from monkey plasma and mouse kidney, has been studied for its substrate specificity and mechanism of action as part of an effort to develop antineoplastic nucleoside analogs that are resistant to enzymic deamination. Steady-state initial rate studies with the enzyme from both sources indicate that uridine is a competitive inhibitor ( K i = 2.8 and 3.4 × 10 −3 M for monkey plasma and mouse kidney deaminase, respectively) with respect to cytidine ( K m = 2.8 × 10 −5 and 1.8 × 10 −4 M for monkey plasma and mouse kidney deaminase, respectively) and ammonium chloride at 2 × 10 −2 M is without inhibitory effect at pH 7.6 or 9.5. The reaction sequence is consistent with a mechanism in which cytidine is the first substrate to interact with the enzyme with the release of uridine as its second product. 1-Methyl-Ψ-isocytidine serves as a substrate; Ψ-isocytidine and 3-deazacytidine do not. Furthermore, Ψ-isocytidine, 2′-deoxy-Ψ-isocytidine and ara-Ψ-isocytosine are potent competitive inhibitors with respect to cytidine in the deaminase reaction ( K i = 7.5 × 10 −5 M, 1.2 × 10 −5 M and 9.2 × 10 −6 M, respectively, for the deaminase from monkey plasma). From substrate specificity and inhibition studies, a mechanism of enzymic deamination of cytosine nucleosides had been proposed which suggests an electrophilic attack by the enzyme at the N-3 position of cytidine which causes electron deficiency at C-4 in the enzyme-substrate complex. Subsequent nucleophilic attack by water at the C-4 position would allow the elimination of ammonia and the dissociation of the enzyme to release uridine as its final product.

Nucleosides. 145. Synthesis of 2,5′-Anhydro-2-Thiouridine and its Conversion to 3′-O-Acetyl-2,2′-Anhydro-5′-Chloro-5′-Deoxy-2-Thiouridine. Studies Directed Toward the Synthesis of 2′-Deoxy-2′-Substituted arabino Nucleosides (7)

Abstract In an attempt to introduce a substituent at C-2′ in the “up” arabino configuration directly by nucleophilic displacement reaction of a preformed pyrimidine ribonucleoside, we synthesized 2,5′-anhydro-5′-deoxy-2-thiouridine (6) in three steps from uridine. Compound 6 was converted into the 3′-O-acetyl derivative 7. Upon treatment of 7 with triflyl chloride in methylene chloride in the presence of triethylamine and p-dimethylaminopyridine, 2,2′-anhydro-1-(3-O-acetyl-5-chloro-2,5-dideoxy-β-D-arabinofuranosyl)-2-thiouracil (9) was obtained as the only isolable product. Obviously, the intermediate 3′-O-acetyl-2,5′-anhydro-2′-O-triflyl-2-thiouridine (8) was attacked by the chloride nucleophile at C-5′ first giving the 2′-O-triflyl-2-thiouridine intermediate from which 9 was formed by intramolecular nucleopilic reaction.

Polydeoxyaminohexopyranosylnucleosides. Synthesis of 1-(2,3,4-Trideoxy-3-nitro-β-D-erythro- and threo-hexopyranosyl)-uracils from Uridine 1

Abstract The first synthesis of nitro-multideoxy-sugar containing nucleosides was achieved. 1-(4,6-O-Benzylidene-3-deoxy-3-nitro-β-D-glucopyranosyl)uracil (3) was converted in 75% yield into 1-(4,6-O-benzylidene-2,3-dideoxy-3-nitro-arabinohexopyranosyl)uracil (7) by acetylation followed by NaBH4 reduction in methanol. De-O-benzylidenation with CF3CO2H afforded crystalline 1-(2,3-dideoxy-3-nitro-β-D-arabinohexopyranosyl)uracil (S) was obtained in 87% yield. Raney Ni reduction of 8 afforded the corresponding 3′-amino-nucleoside 9. Acetylation of 8 followed by NaBH4 treatment afforded an 8:1 mixture from which 1-(2,3,4-trideoxy-3-nitro-β-D-threohexopyranosyl)-uracil (14) was obtained in pure crystalline form. After Raney Ni reduction of the mixture, 1-(3-amino-2,3,4-trideoxy-β-d-threo-hexopyranosyl)uracil (16) and its erythro epimer 21 were isolated. 1-(4,6-O-Benzylidene-2,3-dideoxy-3-nitro-β-d-lyxohexopyranosyl)uracil (24) was prepared in 72% yield from 1-(4,6-O-benzylidene-3-deoxy-3-nitro-β-d-galactopyrano...

A Synthesis of 2’-Fluoro- and 3’-Fluoro-Substituted Purine Nucleosides via a Direct Approach

There are many examples of purine nucleosides fluorinated in the 2′- and 3′ -positions of the sugar moiety (Figure 1) that are making an impact in chemistry, biochemistry, and drug development.

NUCLEOSIDE 66. MITT. SYNTH. AN NUCLEOSID-ANTIBIOTICA 4. MITT. SYNTH. VON METHYL-4-AMINO-2,3,4-TRI-DESOXY-ALPHA-D-ERYTHRO-HEX-2-ENOPYRANOSIDURONSAEURE, DEM KOHLENHYDRAT-ANTEIL DES BLASTICIDIN S

Die Uronsaure (II), der Kohlenhydratanteil des Antibioticums Blasticidin S (I), wird, ausgehend von 6-O-Trityl-4-azido-a-D-glucosid (IIIa), hergestellt.