Acylation propargyl amines

Scheme 13 shows additional examples of constructions of four-carbon chains functionalized appropriately for condensation to pyrroles. Af,Af-bis(trimethylsilyl)propargyl amines can be converted to ketones or esters by lithiation and acylation. These compounds then undergo cuprate addition. The resulting allenyl silyl ethers cyclize to pyrroles on treatment with acid <93T4603). 

C.-Q. Ren, C.-H. Di, Y.-L. Zhao, J.-P. Zhang, [3 + 2] cycloadditions of a-acyl ketene dithioacetals with propargyl amines pyrrole synthesis in water. Tetrahedron Lett. 54 (2013) 1478-1481. 

In a total synthesis of mycalamide B, the aminal unit (63) was prepared from glucose derivative (61) via the key intermediates indicated in Scheme 14. Amongst much ingenious chemistry, the introduction of the axial dimethyl acetal grouping into (62) by the use of propargyl trimethylsilane-TMSOTf, followed by ozonolysis and acetalization, is noteworthy. Hydroxyl-ation of the allyl group involved asymmetric osmylation the synthesis was completed by acylation of (63) with a non-sugar-derived acid unit, and mycalamide A was made by a variation on the route.4... 

The synthesis began with the preparation of amine 148 from propargyl alcohol (147). Acylation of the amine with 149 gave 146, and the proposed Diels-Alder reaction proceeded smoothly to give 144. The remote double bond of 144 was the most electrophilic double bond and thus, epoxidation from the sterically most accessible face gave 150 as the major product. 

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