Synthesis of the Enantiomerically Enriched Macrocyclic Lactones (+)‐(<i>S</i>)‐ and (−)‐(<i>R</i>)‐Phoracantholide I and (+)‐(<i>S</i>)‐Tetradecan‐13‐olide

Abstract

Abstract Synthesis of two naturally occurring macrocyclic lactones is described. (−)‐( R )‐Phoracantholide I ((−)‐ 1 ; Scheme 2 ) was synthesized by asymmetric and chemoselective reduction of the side‐chain CO group of (−)4‐(1‐nitro‐2‐oxocyclohexyl)butan‐2‐one ((−)‐ 6 ) with ( R )‐ Alpine‐Hydride (47% ee). It was shown that the formation of only one diastereoisomer of the hemiacetal 5 , by methylation with (i‐PrO) 2 TiMe 2 of ketoaldehyde (−)‐ 2 is thermodynamically controlled. (+)‐( S )‐Tetradecan‐13‐olide ((+)‐ 10 ) was obtained by reduction of diketone (±)‐ 11 with optically active borohydrides followed by denitration ( Scheme 3 ).