Synthesis of 3'-deoxy-3'-fluorokanamycin A and 3',4'-dideoxy-3'-fluorokanamycin A

Site-Selective Palladium-catalyzed Oxidation of Unprotected Aminoglycosides and Sugar Phosphates

The site-selective modification of complex biomolecules by transition metal-catalysis is highly warranted, but often thwarted by the presence of Lewis basic functional groups. This study demonstrates that protonation of amines and phosphates in carbohydrates circumvents catalyst inhibition in palladium-catalyzed site-selective oxidation. Both aminoglycosides and sugar phosphates, compound classes that up till now largely escaped direct modification, are oxidized with good efficiency. Site-selective oxidation of kanamycin and amikacin was used to prepare a set of 3'-modified aminoglycoside derivatives of which two showed promising activity against antibiotic-resistant E. coli strains.

Synthesis of kanamycin A analogs containing a 6-amino-6-deoxyglycofuranose moiety

Three kanamycin A analogs containing 6-amino-6-deoxyglycofuranoses have been prepared as candidates for potential activity against resistant bacteria producing 6'-N-acetyltransferase. They are 4-O-(6-amino-3,5,6-trideoxy-alpha-D-, -beta-D-, and -beta-L-erythro -hexofuranosyl)-6-O-(3-amino-3-deoxy-alpha-D-glucopyranosyl)-2,5-dideoxy-5-epi-5-fluorostreptamine. Structure-activity relationships of these compounds are discussed.

Synthesis of alpha,alpha-, alpha,Beta-, and Beta,Beta-(dimaltoside)s of ethane-1,2-diol, propane-1,3-diol, and butane-1,4-diol: a proposal for an initial adhesion mode

Nine dimaltoside derivatives of ethane-1,2-diol, propane-1,3-diol, and butane-1,4-diol having the alpha,alpha, alpha,beta, and beta,beta anomeric configurations at the linkage sites have been synthesized. Suitably protected maltosyl halides or a 1-(phenylthio) derivative were condensed with the foregoing diols and the resulting monomaltosyl derivatives were further condensed with the maltosyl donors to give, after deprotection, the title compounds. Their structures were fully characterized by NMR spectroscopy. Interactions between the three alpha,alpha-(dimaltoside)s and cinnamyl alcohol are briefly discussed.

Synthesis of 2"-oxidized derivatives of 5-deoxy-5-epi-5-fluoro-dibekacin and -arbekacin, and study on structure-chemical shift relationships of urethane(or amide)-type NH protons in synthetic intermediates

Three 2"-modified dibekacin-analogs have been prepared as potential compounds active against resistant bacteria producing 2"-O-phosphotransferases; one is 5-deoxy-5,2"-diepi-5-fluorodibekacin (9) prepared from a suitably protected 2"-O-triflyl derivative through the 2" 3"-cyclic carbamate, and the others are 2"-oxo derivatives (12 and 22, both as the hydrate) of 5-deoxy-5-epi-5-fluoro-dibekacin and -arbekacin prepared through oxidation at C-2" of suitably protected derivatives. Relationships between the t-butoxycarbonyl(= Boc)-NH-shifts of per-N-Boc synthetic intermediates and their structures were studied. It was found that the shifts, measured in pyridine-d5 at 80 degrees C, which spread over a close range (delta 6-7 ppm), are sensitively influenced by nearby and surrounding groups around the BocNH group in respect of electron-withdrawing character, hydrogen bonding (BocNH ... acceptor), and also solvent effects (BocNH ... NC5H5).

Synthesis of dibekacin analogs containing 3-oxa- and 3-aza-2,3,4-trideoxy-D-glycero-hexopyranose

6-O-(3-Oxa-2,3,4-trideoxy-alpha-D-glycero-hexopyranosyl) derivatives (10 and 17) of both 3',4'-dideoxyneamine and 5-epifluoro-5,3',4'-trideoxyneamine have been prepared by coupling ethyl 6-O-benzyl-3-oxa-2,3,4-trideoxy-1-thio-D-glycero-hexopyranoside (5) with suitable aglycons. The corresponding 3"-aza derivative (19) of dibekacin (6) was prepared by oxidation of 1,3,2',6'-tetra-N-tosyldibekacin (7) with Pb(OAc)4 followed by treatment with NH4OAc and reduction with NaBH3CN. Related ring-opening compounds (11 and 25) were also prepared.

Synthesis of kanamycin A analogs containing 6-amino-3-oxa-2,3,4,6-tetradeoxy-D- and -L-glycero-hexopyranose

6-Azido-3-oxa-2,3,4,6-tetradeoxy-D- and -L-glycero-hexopyranoses were synthesized in five steps from (2S)-and (2R)-1,2-O-isopropylideneglycerols, respectively. After conversion into the corresponding ethyl 1-thioglycosides, each was condensed with a protected derivative of 6-O-(3-amino-3-deoxy-alpha-D-glucopyranosyl)-2-deoxystreptamine (16). Deprotection and reduction of the azido group of the condensation products gave the title compounds.

Synthesis of 5-deoxy-5-fluoro and 5-deoxy-5,5-difluoro derivatives of kanamycin B and its analogs. Study on structure-toxicity relationships

5-Deoxy-5-fluoro- (1), 5.3'-dideoxy-5-fluoro- (2), and 5,3',4'-trideoxy-5-fluoro-kanamycin B (3) have been prepared by treatment of 5-epihydroxyl precursors (prepared by the Mitsunobu reaction) with DAST as the key step. 5,3'-Dideoxy-5,5-difluoro- (26) and 5,3',4'-trideoxy-5,5-difluoro-kanamycin B (27) were also prepared by treatment of the corresponding 5-oxo derivatives with DAST. These 5-deoxy-5-fluoro and 5-deoxy-5,5-difluoro derivatives showed markedly decreased toxicity as compared with the parent compounds.

Synthesis of 4'-deoxy-4'-fluorokanamycin A and B

4'-Deoxy-4'-fluorokanamycins A (17) and B (25) have been prepared through fluorinative ring-opening of the D-galacto-3',4'-oxiranes (8 and 21) derived from kanamycin A and B with potassium hydrogenfluoride in ethane-1,2-diol. The mechanism of preponderant formation of the 4'-deoxy-4'-fluoro-D-gluco (9 and 22) over the 3'-deoxy-3'-fluoro-D-gulo derivatives was discussed. In the synthesis of 25, the unusual 3',6'-epimine (23) was the main product along with the 4'-deoxy-4'-fluoro derivative. The mechanism of this reaction is also discussed. Both 17 and 25 were active against resistant bacteria producing aminoglycoside-adenylylating enzymes for HO-4'.

Study on fluorination of 2,3-dideoxy-2,3-(N-tosylepimino)-alpha-D-allopyranosides, and synthesis of 3'-deoxy-3'-fluorokanamycin B and 3',4'-dideoxy-3'-fluorokanamycin B

Reaction of the structurally rigid methyl 2,3-dideoxy-4,6-O-isopropylidene-2,3-(N-tosylepimino)-alpha-D-a llopyranoside (6) with KHF2 in DMF at 150 degrees gave initially methyl 2,3-dideoxy-2-fluoro-4,6-O-isopropylidene-3-tosylamido-alpha-D-altrop yranoside (10) by N-tosylepimine-ring opening, and 10 was gradually converted into the stable methyl 2,3-dideoxy-3-fluoro-4,6-O-isopropylidene-2-tosylamido-alpha-D-glucopyra noside (11). A reversible mechanism involving 6 and 10 has been proposed. In the mobile methyl 2,3-dideoxy-2,3-(N-tosylepimino)-alpha-D-allopyranoside (7) and the corresponding 4,6-di-O-acetyl (8) and -di-O-methyl derivatives (9), reactions with KHF2 proceeded comparatively rapidly giving the corresponding 3-deoxy-3-fluoro-alpha-D-glucopyranosides as the major products. A slightly different reaction mechanism for the mobile compounds has been proposed. By application of this study, 3'-deoxy-3'-fluorokanamycin B was prepared by treatment of 4",6"-O-cyclohexylidene-2'-deamino-3'-deoxy-3'-epi-6'-N-methoxycarbonyl- 1,3, 3"-tri-N-tosyl-2',3'-(N-tosylepimino)kanamycin B (21) with KHF2 as the key reaction. 3',4'-Dideoxy-3'-fluorokanamycin B was also prepared. Both compounds were active against resistant bacteria producing 3'-modifying enzymes.

A synthetic study of methyl 3-deoxy-3-fluoro-alpha-D-glucopyranosides from methyl 2,3-anhydro-alpha-D-allopyranosides, and synthesis of 3'-deoxy-3'-fluorokanamycin A and 3'-chloro-3'-deoxykanamycin A

Reactions of 4,6-disubstituted 2,3-anhydro-alpha-D-allopyranosides with potassium hydrogenfluoride (KHF2) in ethane-1,2-diol gave, by oxirane-ring opening, the corresponding 2-deoxy-2-fluoro-alpha-D-altro- and 3-deoxy-3-fluoro-alpha-D-gluco-pyranosyl derivatives, with the latter always in preponderance. The influence of the substituents at C-4 and C-6 on the D-gluco-D-altro ratio (r) have been studied by molecular mechanics, and the discrepancy between the experimental and calculated r values has been positively utilized to measure the effects of solvation and hydrogen bonding relative to the C-4 and C-6 substituents. By application of this reaction, 3'-deoxy-3'-fluorokanamycin A has been prepared by treatment of a 2',3'-anhydro-3'-epikanamycin A derivative (35) with KHF2. 3'-Chloro-3'-deoxykanamycin A was also prepared.