Synthesis of β-Tubanol

Synthesis of β-tubanol (VIa) was achieved by the bromination of dihydro-β-tubanol acetate (VIIb) followed by dehydrobromination and the subsequent hydrolysis. 2,2-Dimethyl-5-hydroxy-chromanone as well as its derivatives (IV) and the corresponding chromanols (V) and chromans (VII) were also prepared.     

Synthesis of (−)‐DAPD

A new synthesis of (?)‐DAPD, suitable for large scale development, is described.     

Synthesis of 7β-hydroxy-epiandrosterone

The synthesis of 7β-hydroxy-epiandrosterone (6) possessing strong anti-inflammatory properties was achieved starting from 3β-acetoxy-17,17-(ethylenedioxy)-5-androsten (1). This approach involved as a main step an allylic oxidation of the C-7 followed by two reduction reactions of the double bond and of the carbonyl group. This stereoselective synthesis in 5 steps gave 7β-hydroxy-epiandrosterone in 63% overall yield.     

Synthesis of Isochroman-1,3-diones A New Synthesis of (±)Sclerin

(±)Sclerin (4,5,6,7-tetramethyl-8-hydroxyisochroman-1,3-dione), a mycerial extracts of Sclerotinia libertiana, and related compounds were synthesized. Alkylated-7-hydroxyindanones were obtained from alkylated phenols and α-bromobutyrylbromide, and these indanone derivatives were treated with benzaldehyde to give 2-benzylidene-7-hydroxyindanone derivatives. By ozonolysis of these benzylidene-indanones were obtained 8-hydroxyisochroman-1,3-diones.     

Synthesis of (±)-licarin-B

The synthesis of (±)-licarin-B, a neolignan of Licaria aritu Ducke (Lauraceae), was achieved by pyrolysis of 3-hydroxy-3-piperonyl-1-propyl-2-methoxy-4-(E)-propenylphenyl ethers.     

The Synthesis of αβ Imidothymidine Diphospate

Abstract

It has been shown by many workers that nucleotides containing an ap methylene link have interesting biochemical properties compared to those containing an αβ 0x0 linkage.¹ In our laboratory af3 methylene thymidine triphosphate has been shown to be a more powerful inhibitorof thymidine kinase than thymidine triphosphate but a weaker inhibitor of ribonucleotide reductase and cytidine deaminase. We have been interested in examining the properties of the af3 imido analogue. Several routes to prepare the unknown ap imidothymidine triphosphate were unsuccessfully tried:

1. Reaction of 3′-O-Acetylthymidine with the tributylammonium salt of dicyclohexylcarbodiimide.

2. Reaction of 5′-O-tosylthymidine with the tributylammonium salt 3 of imidodiphosphoric acid in hot dimethylacetamide.

     

Synthesis of (–)-Muricatacin

The synthesis of (–)-muricatacin starting from 1-bromododecane and 2-pentyn-l-ol is described. 2-Pentadecyn-1-ol (4), which was prepared from 1-bromododecane (2) and 2-pentyn-1-ol (3), was converted to epoxy alcohol 6 through a two-step reaction sequence, 6 being successively submitted to tosylation, iodination, chain extension with tert-butyl lithioacetate, and acid-catalyzed cyclization to give (–)-muricatacin (1a). Recrystallization afforded optically pure 1a.     

Synthesis of L-3′-Hydroxymethylribonucleosides

Abstract

The target compounds were synthesized via the key intermediate carbohydrate 8, which was synthesized by first selectively protecting the 1′ - and 2′- hydroxyl groups followed by selective tosylation of the 5′ -hydroxyl group to obtain compound 3. The tosyl moiety was then replaced by a benzyl ether to obtain 4. Compound 4 underwent Dess-Martin oxidation to afford the ketone 5. Compound 5 was subjected to Wittig olefination to afford the alkene 6 followed by regioselective hydroboration to obtain 7. Compound 7 was fully acetylated using acetic acid, acetic anhydride and sulfuric acid to obtain the key intermediate 8.     

The Synthesis of Dilnethyl α-Sorigenin

1,6,8-Trimethoxy-3-hydroxymethyl-2-naphthoic acid lactone (IV) was synthesized from benzoic acid in 21 steps. This lactone (IV) was completely identical with authentic dimethyl α-sorigenin, obtained by the methylation of natural α-sorigenin. Herewith the structure of α-sorigenin was confirmed to be 1,8-dihydroxy-6-methoxy-3-hydroxymethyl-2-naphthoic acid lactone (III).     

A New Synthesis of α-Methylspermidine

A five-step synthesis of -methylspermidine (1,8-diamino-5-azanonane), the first polyamine analogue preventing pathological consequences of spermidine depletion in transgenic rats overproducing spermine/spermidine N ¹-acetyltransferase, from ethyl 3-aminobutyrate was achieved in a high overall yield.     

Stereoselective Synthesis of Carbocyclic α-L-Homonucleosides

Abstract

The synthesis of several optically pure carbocyclic α-L-isomeric homonucleosides [3a-e, 6a,b, 7a,b, 10a-d] is reported. The (1R, 5S)-2-oxabicyclo[3.3.0]oct-6-en-3-one 1 was used as a chiral starting material.     

Synthesis of (±)-Xanthoxins

The enzymatic properties of P2-2 enzyme were determined by using cells of M. radiodurans. The enzyme was: most active at 60°C incubation temperature, stable at 40°C in neutral buffer, and inactivated by heating at 80°C for 15min. Maximal lytic activity occurred at pH 8.5 in Tris-HCl buffer. The range of enzyme stability was between pH 5.5 and 8. Bivalent metal ions, p-chloromercuribenzoate and monoiodo acetate inhibited lytic activity. The molecular weight was estimated to be 16,000 daltons by gel filtration on Sephadex G-75. The enzymatic digestion of peptidoglycans from the cell walls of M. radiodurans and M. lysodeikticus liberated free amino groups, but neither reducing groups nor N-acetylhexosamine, indicating that the enzyme was an endopeptidase. From analysis of the N-terminal amino acids of the digests, it is suggested that the P2-2 enzyme cleaves the peptide bond at the carboxyl group of D-alanine in peptidoglycan.     

A Facile Synthesis of ε-Pyridoxinyl-L-Iysines

The intracellular cadmium (Cd) content was measured with early stationary phase cells of a highly Cd-tolerant moderately halophilic bacterium Pseudomonas sp. No. 40 cultivated in 1M and 3M NaCl medium containing 0 to 2500 μg of CdCl₂/ml. It was found that the Cd contents were greatly affected by the NaCl concentration of the medium. When the bacterium was cultivated in the 1, 2, 3, and 4M NaCl medium containing 1500 μg of CdCl₂/ml, the intracellular Cd content was 25.0, 4.1, 3.1, and 2.0 mg Cd per g of dry cells, respectively. The intracellular Cd content decreased with increases of NaCl concentration of the medium. The fact seems to reflect Cd-tolerance of the bacterium towards the growth in the medium of different NaCl concentration. It is worthwhile to note that the bacterium showed the highest Cd-tolerance (in 3M NaCl) and the lowest Cd content among the bacteria so far known. The bacterial cells grown in the 1M NaNO₃ and 1M Na₂SO₄ medium accumulated 1.8–1.3 times as much Cd²⁺ as those in the 1M NaCl medium in the presence of 50–200 μg of CdCl₂/ml. It would also explain the difference in the Cd toxicity in the medium of NaNO₃, Na₂SO₄, or NaCl.     

Synthesis of citrate–ciprofloxacin conjugates

Two regioisomeric citrate-functionalized ciprofloxacin conjugates have been synthesized and their antimicrobial activities against a panel of clinically-relevant bacteria have been determined. Cellular uptake mechanisms were investigated using wild-type and ompF deletion strains of Escherichia coli K-12.     

Synthesis of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine Aryl β-Glycosides

Synthesis of N-acetylmuramyl-L-alanyl-D-isoglutamine phenyl and (2-naphthyl) -glycosides, novel muramyl dipeptide derivatives with phenolic aglycons, was reported. The starting N-acetylglucosamine aryl glycosides were obtained by glycosylation of phenols with peracetylated -glucosaminyl chloride under the conditions of phase-transfer catalysis and used for the synthesis of 4,6-O-isopropylidene-N-acetylmyramic acid aryl -glycosides. Condensation of these derivatives with a dipeptide and subsequent deprotection resulted in the intended glycopeptides.     

Synthesis of biheterocyclicα-amino acids

Summary We report here the synthesis of biheterocyclic-amino acids by 1,3 dipolar cycloaddition of acetylenic compounds on-azido-amino esters.     

Synthesis of (±)-Hydroxytremetone

(±)Hydroxytremetone (III) has been synthesized from 2-(α-hydoxyisopropyl)-6-hydroxycoumaran (V b) via its O-acetate V c by dehydration with phosphorus tribromide in pyridine solution, followed by acylation with a mixture of trifluoroacetic anhydride and acetic acid. Isohydroxytremetone (IX b) was also synthesized.