An efficient seven-step, protecting-group-free first total synthesis of chatenaytrienin-2 based on ring-closing metathesis and C(sp)−C(sp 3 ) Sonogashira coupling with a 36.5% overall yield has been described. The ready availability of starting materials and key Wittig olefination, ring-closing metathesis, Lindlar reduction, and C(sp)−C(sp 3 ) coupling makes this strategy applicable for the synthesis of various unbranched polyene-natural products with 1,5,9,n-(Z)-configured double bonds.

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A de novo protecting-group-free total synthesis of (+)-muricadienin, (+)-ancepsenolide and (+)-3-hexadecyl-5-methylfuran-2(5H)-one has been achieved. Ring-closing-metathesis has been the key step in the synthesis. In (+)-muricadienin synthesis, a long chain alkyl group has been installed by an sp-sp Sonogashira type reaction followed by a cis-selective Lindlar reduction. The total synthesis is achieved in 7 steps and in excellent 43.5% overall yield. Similarly, (+)-ancepsenolide and (+)-3-hexadecyl-5-methylfuran-2(5H)-one synthesis is completed in 5 steps each and in 48 and 68% overall yields, respectively.

The b-hydroxy-g-lactones, cardiobutanolide and Hagen's gland lactones have been interesting targets for total synthesis in many laboratories. There are 10 syntheses reported for cardiobutanolide and 19 syntheses for Hagen's gland lactones. These natural products have the b-hydroxy-g-lactone moiety in common. The evolution of various synthetic strategies to these natural products from chiral pool materials and/or asymmetric catalysis and involving linear sequences, convergent approaches to the de-novo protecting group free syntheses have been abstracted in this review.[a] Prof.