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A convenient method for synthesis of 2R,3S and 2S,3S N-Boc phenylalanine epoxides using readily available allylamine is described. Previous methods employed multistep synthetic routes from l-phenyl alanine that include use of m-chloroperbenzoic acid (m-CPBA) and a chromatographic method for purification of the desired diastereomers. Column purification could be eliminated by bringing in much improvement in the existing process. The process was further enhanced by replacing m-CPBA with oxone, an ecofriendly reagent advantageous for commercial application. The overall green process discussed involves the recovery and recycling of enantiomers of chiral allyl amines and judicial separation of diastereomers of the epoxides using simple economical methods.

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magnified image 1,3‐Dipolar cycloadditions of benzonitrile oxide and carbethoxyformonitrile oxide (CEFNO) with various facially perturbed polycyclic symmetrical dienophiles (1, 1a, 1b, 2, 2a, 2b, 3, 3b, 4, 5, 6) were investigated. Cycloadditions took place chemoselectively at the norbornyl double bond and were found to be exclusively exo. Cycloadditions of benzonitrile oxide with dienophiles 4 and 5 led to mixture of inseparable products, however, that with CEFNO gave single products. Cycloadduct of dienophile 5 with CEFNO was found to be unstable, and it readily isomerized to more stable aromatic form. J. Heterocyclic Chem., (2010).

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Isoxazole conjugates of sugar have been synthesized by the aid of 1,3-dipolar cycloaddition in a click chemistry approach. The sugar-derived propargyl ethers underwent 1,3-dipolar cycloadditions smoothly with in situ generated nitrile oxides from aromatic oximes in good yields. The reaction exhibited a high degree of regioselectivity.Key words: isoxazole conjugates, 1,3-dipolar cycloadditions, nitrile oxides.

1,3-Dipolar Cycloaddition of Nitrile Oxides with Symmetrical Tri-and Polycyclic Strained Olefins. -1,3-Dipolar cycloadditions of in situ generated nitrile oxides with various polycyclic dienophiles are studied. The reactions take place chemoselectively at the norbonyl double bond and yield exclusively exo products. The symmetrical polycyclic compound (VIII) with four -faces gives the corresponding monoadducts stereoand chemoselectively. -(DARVATKAR, N. B.; WANKHEDE, K. S.; BHILARE, S. V.; DEORUKHKAR, A. R.; RAUT, D. G.; VAIDYA, V. V.; TRIVEDI, G. K.; SALUNKHE, M. M.; J.