Thymine polyoxin

Transformation of chiral nitrones into enantiomer enriched a-chiral N -hydroxylamines and their derivatives, has been successfully employed in the enantioselective synthesis of (+ )-(R)- and (—)-(S)-zileuton (216). An expeditious synthesis of thymine polyoxin C (347), based on the stereocontrolled addition of 2-lithiofuran (a masked carboxylate group) to the A-benzyl nitrone derived from methyl 2,3-O-isopropylidene-dialdo-D-ribofuranoside, is described (Scheme 2.151) (194). 

Antifungal antibiotic (+ )-polyoxin J can be obtained in 46,4% yield by combining the derivative of 5-O-carbamoylpolyoxamic acid (348) with thymine polyoxin C (347) (Scheme 2.152) (196, 583)... 

The reaction of silyl ketene acetal addition to nitrones has been used for the synthesis of optically active (2S,3S)-benzoyl- and /V- oc-phenyl isoserine (636a) of isoxazolidine nucleoside-analog of thymine polyoxine C(636b) and of... 

This method was used in the synthesis of thymine polyoxin C [38]. A similar method was also used in the synthesis of 5-aminohexofuranoses (see Sec. I1I.B). 

P. Gamer and J. M. Park, Glycosyl ot-amino acids via stereocontrolled buildup of a penaldic acid equivalent. An asymmetric synthesis of thymine polyoxin C, Tetrahedron Lett. 30 5065 (1989). 

The synthesis of (-t-)-polyoxin J 14 is completed by selective ester hydrolysis with aqueous lithium hydroxide. The resulting carbamoylpolyoxamic acid was then coupled with the protected thymine polyoxin C 8 with the BOP reagent (Castro s reagent)14 (benzotriazol-1 -yloxytris(dimethyl-amino)phosphonium hexafluoro-phosphate) 37 to furnish the peptide derivative in 63 % yield. 

The stereoselective synthesis of (+)-polyoxin J is accomplished by Gosh in 24 steps and 3 % overall yield. The key intermediates are protected thymine polyoxin C 8 and the 5-Ocarbamoyl polyoxamic acid 2, which were synthesized from D-ribose and dimethyl L-tartrate. Key steps are two different epoxidation reactions, one carried out with MCPBA and the other under Sharpless conditions with the D-(-)-tartrate. Both epoxides are opened with diisopropoxytitanium diazide. The coupling of the two fragments was realized with the BOP reagent 37. This synthesis provides an easy access to the synthesis of various (+)-polyoxin J analogs for biological evaluation. 

Sulphoxides, sulphates and sulphonyl compounds have also been used as substrates in stannane-mediated reductions. Gethin and Simpkins reported the Bu3SnH-mediated removal of the tosyl group in substrate (79) in their preparation of protected thymine polyoxin C (equation 53)293. Similarly, Xu and Lu described the removal of the tosyl group in 80 under similar conditions during their synthesis of pentabromopseudilin (equation 54)294. Padwa and his associates utilised B SnH to remove the sulphone moiety in cyclopentenone (81) (equation 55)295, while Wnuk and coworkers discuss... 

Chen, A., Savage, I., Thomas, E. J., Wilson, P. D. Asymmetric a-amino acid synthesis using [3.3] rearrangement of allylic trifluoroacetimidates synthesis of thymine polyoxin C. Tetrahedron Lett. 1993, 34, 6769-6772. 

Total syntheses of thymine polyoxin C and polyoxin have been reported. Syntheses have also been reported for neosidomycin 8 and the related antibiotic SF-2140 9, thereby confirming their structures. ... 

Degradation of polyoxin D yielded uracil polyoxin C, 30, which was used to prepare analogues of both polyoxins and nikkomycins. Thymine polyoxin C has been synthesized. N.m.r. data on polyoxin A have suggested a revised stereochemistry for the exocyclic double bond... 

T. Nishiyama, S.S. Mobile, T. Kajimoto, M. Node, Synthesis of thymine polyoxin C by using L-threonine aldolase-catalyzed aldol reaction. Heterocycles 71 (2007) 1397-1405. 

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