Jack J. Fox

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.

Spectrophotometric studies of nucleic acid derivatives and related compounds as a function of pH. IV. On the structure of orotidine. A study of N-methylated orotic acids.

Abstract In order to provide a firm basis for the determination of the position of attachment of the sugar moiety to the pyrimidine ring in orotidine, a series of N-methylated orotic acid derivatives have been synthesized and their structure proved by conversion to substances of known structure. The ultraviolet absorption spectra of these N-methylorotic acid derivatives as a function of pH were determined and their “apparent” dissociation constants were measured spectrally. It was shown that these derivatives bear the same spectral relationship to orotic acid as do the N-methylated uracils to uracil. Information relative to the structure of these compounds in aqueous solutions was deduced therefrom. The spectrum of orotidine as a function of pH was presented and shown to be very similar to that for 1-methylorotic acid. The sugar residue of orotidine (and thereby of orotidine-5′-phosphate) is therefore linked at the #1 position of the pyrimidine ring. Metaperiodate oxidation studies have shown that orotidine is a furanoside. The structure of orotidine is, therefore, 1- d -ribofuranosyluracil-6-carboxylic acid.

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.

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 : XXX. Synthesis of 2-deoxy-2-fluoro-D-ribose

Abstract Crystalline 2-deoxy-2-fluoro- D -ribose (IVb) was prepared by debenzoylation of 1,3,4-tri-O-benzoyl-2-deoxy-2-fluoro-β- D -ribose (VIb). Reduction of 2′-deoxy-2′-fluorouridine (Ib) gave amorphous 1-(2-deoxy-2-fluoro-β- D -ribofuranosyl)-5,6-dihydrouracil (IIb), which was converted into crystalline 1-(3,5-di-O-benzoyl-2-deoxy-2-fluoro-β- D -ribosyl)-5,6-dihydrouracil (III). Glycosylic cleavage of IIb with dilute alkali, followed by heating with dilute acid, gave a mixture containing IVb. Benzoylation of impure IVb produced crystalline VIb. A second product, in amorphous form, probably 1,3,4-tri-O-benzoyl-2-deoxy-2-fluoro-α- D -ribose, was isolated; it also gave crystalline IVb upon debenzoylation. The pyranoid structure of VIb was proved as follows: replacement of the benzoyloxy group on C-1 by a methoxyl group gave methyl 3,4-di-O-benzoyl-2-deoxy-2-fluoro- D -riboside (VIII). Debenzoylation gave the unsubstituted glycoside IX, which was shown to be a pyranoside, thus establishing the ring structure of VIb. Methanolysis of IIb, followed by benzoylation, gave crystalline methyl 3,5-di-O-benzoyl-2-deoxy-2-fluoro- D -riboside (X) and amorphous VIII, as well as crystalline methyl 3-(N-benzoylureido)propionate (XII). Debenzoylation of X produced crystalline methyl 2-deoxy-2-fluoro- D -ribofuranoside (XI).

Nucleosides XCIII. Synthesis of 6-β-d-ribofuranosyl-pyrmidines (a new class of pyrimidine c-hucleosides)☆

Aus dem geschutzen Ribosederivat (Ia) entsteht das Chlorid (Ib), das mit Silberpropiolat (II) zum Addukt (III) fuhrt.

Nucleosides. XLI. The conformation of 1,3,4-tri-O-benzoyl-2-deoxy-2-fluoro-β-d-ribose and of 1,3,4-tri-O-benzoyl-2-deoxy-α-(and β-)-d-erythro-pentose

Abstract N.m.r. studies have been conducted on 1,3,4-tri- O -benzoyl-2-deoxy-2-fluoro-β- d -ribose ( 1 ) and on the β and α anomers of 1,3,4-tri- O -benzoyl-2-deoxy- d - erythro pentose ( 2 and 3 , respectively). Temperature studies have shown that all exist as pure conformers having an axially oriented aglycon. The conformation of 1 and 2 was established as 1C , that of 3 as C1 .