Oxetanocins

The five oxetanocins were tested against hepatitis B virus (HBV). Oxetanocin G and 2-aminooxetanocin A showed to be more potent than the lead compound, with ID50 values of 0.72 and 0.32 pg/ml, respectively, and therapeutic indexes of 139 and 156, respectively, thus being 12-27 time stronger than the reference drug ara-A. It was also proposed that oxetanocins likely affect HBV-related reverse transcriptase [205]. 

However, in spite the interesting antiviral activity shown by oxetanocins, studies on their biosynthesis were limited since the oxetanocin A productivity of the strain was very low and unstable. Mutants producing high quantities of oxetanocin A were isolated from the original B. megaterium strain NK84-0228, but the productivities 

FOUR-MEMBERED HETEROCYCLIC RINGS AND THEIR FUSED DERIVATIVES 

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Chiral cyclobutanes can be prepared by cycloaddition of alkenes substituted with one or more chiral auxiliary groups. A diastereofacial selectivity of 95% was observed in the diethylalu-minum chloride catalyzed cycloaddition of 1,1-dimethoxyethene (36) with ( — )-dimenlhyl-3-yl fumarate (37).16 The chiral cyclobutane 38 has been used as an intermediate in the synthesis of carbocyclic oxetanocin analogs. 

Oxetanocin was obtained by carrying out the reaction between 2-methylfuran and benzoyloxyacetaldehyde. The corresponding adduct was treated with ozone, and the product was reduced with NaBPLj. The obtained alcohols were protected. 

Fleet and colleagues have investigated various synthetic approaches for the formation of oxetane nucleosides of which oxetanocin 48 is an important and desirable member.34 The oxetane carboxylic acids 49a are helpful precursors for a-chlorooxetanes 50 via 49b, which in turn provide oxetane... 

A total enantioselective synthesis of antiviral carbocyclic oxetanocins 289 and 290 was also completed by the Ichikawa group by utilizing a... 

Hsiao, C.-N. et al. Efficient Syntheses of Protected (2S,3S)-2,3-Bis(hydroxy-methyl)cyclobutanone, Key Intermediates for the Synthesis of Chiral Carbocyclic Analogues of Oxetanocin. 4.1 1990 [127]... 

Synthesis of oxetanocine, a nucleoside antibiotic with anti-HIV action, and of related compounds 91YGK670. 

Asymmetric [2 + 2] cycloaddition reaction affords a practical means of synthesis of optically active cyclobutanes, which can be used as useful intermediates in organic synthesis [138]. Narasaka reported that asymmetric [2 -i- 2] cycloaddition between acryloyl oxazolidinone derivatives and bis(methylthio)ethylene proceeded with high enantios-electivity when catalyzed by TADDOL-derived titanium complex (Sch. 58) [139]. The cyclobutane product was transformed into carbocyclic oxetanocin analogs or (-n)-grand-isol [140]... 

The natural product (-)-oxetanocin is an unprecedented oxetanosyl-A/-glycoside that inhibits the in vitro replication of human immunodeficiency virus (HIV). In order to prepare multigram quantities of the compound, D.W. Norbeck et al. devised a short and efficient synthetic strategy. The cornerstone of the strategy was the Wolff rearrangement of a five-membered diazo ketone. The diazo transfer was achieved by first converting the ketone to an enamino ketone followed by treatment with triflyl azide. Upon irradiation with a 450 W Pyrex filtered Hanovia lamp, the isomeric oxetanes (a 3 = 2 1) were obtained in 36% yield. 

Syntheses of oxetanocin A (a nucleoside with anti-viral activity) and related unusual nucleosides with / .v(hydroxymethyl)-branched sugars 02S1. 

The cleavage of a terminal )3-phenylsulfonyl silyl group to give a methylenecyclopropane is readily accomplished by treatment with tetrabutylammonium fluoride (TBAF) in tetrahydro-furan. Thus, the bis(benzyl) ether of trani-3-methylenecyclopropane-l,2-dimethanol, trans-, 2-bis[(benzyloxy)methyl]-3-methylenecyclopropane (2), was obtained in 91% yield as part of a synthesis of oxetanocin. ... 

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