Abstract:The aminopalladation of amino allylic alcohol using Cl2Pd(MeCN)2 in CH2Cl2 gave the 2,6-disubstituted piperidine with excellent diastereoselectivity. This compound was successfully converted into (+)-azimine (1) using cross-metathesis and Shiina macrolactonization.

Four diastereomers of tetradenolide, a cytotoxic -pyrone isolated from Tetradenia riparia, were synthesized stereoselectively using Z-selective Horner-Emmons reaction followed by acid catalyzed lactonization. Making comparison of the 1 H and 13 C NMR spectral data of the four diastereomers with those of the reported value of natural product did not lead to determine the relative stereochemistry of the natural tetradenolide. Thus detailed investigation of the spectral data of the related compounds led us to revise the structure of tetradenolide as deacetylboronolide.

(+)-Boronolide and (+)-deacetylboronolide were synthesized using Pd-catalyzed CO insertion and lactonization as the key step. As to the 13 C NMR data of (+)-deacetylboronolide, the assignment at C-6 position should be revised.Key words: natural products, lactones, asymmetric synthesis, total synthesis, carbonylation Due to significant biological activity as well as unique structure, boronolide and its related compounds attracted much attention of many synthetic chemists. 6a-m In the typical examples of asymmetric syntheses of boronolide, Sharpless asymmetric dihydroxylation, 6b asymmetric aldol reaction, 6d,6e and chiral pool approach 6a,6d,6f were used to construct four chiral centers. The typical example of preparation of ,-unsaturated -lactone was done using elimination of selenoxide 6a,6b,6f or ring-closing olefin metathesis. 6e To synthesize ,-unsaturated -lactones, Pdcatalyzed CO insertion and cyclization of (Z)-alkenyl halide is one of the most useful tools. 7 In this paper, we wish to describe concise synthesis of (+)-boronolide (1) and (+)-deacetylboronolide (2) using Pd-catalyzed

Stereoselective synthesis of decytospolide A and B and their C-3 epimers, which have a 2,6-cis-tetrahydropyran ring, has been achieved in high stereoselectivity and yield. The oxypalladation of single diastereomers of 6-(benzyloxy)-7-hydroxydodec-2-enyl 2-naphthoates was optimized to give products with a 2,6-cis-tetrahydropyran ring with high diastereoselectivity and yield.

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