Total Synthesis of Woodwards Carbamate Intermediate

Deslongchamps synthesis is based upon the stereoelectronic controls of the conformation of the l,7-dioxaspiro[5.5]undecane system. The first target of the synthesis was the dioxaspiroundecane derivative 65 of the seco-acid methyl ester, which had been derived from erythromycin A (46) by his group. 

Condensation of the lactone 56 with the lithiated acetylide of optically active 57 followed by silylation and hydrogenation gave 58. 

The olefin 58 was cyclized to give, after equilibration at Cg, the optically active spiro diester 59, which was converted into the bispropionate 61 through 

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