[reaction: see text] The Cu(I)-catalyzed cycloisomerization of tertiary 5-en-1-yn-3-ols with an 1,2-alkyl shift affords stereoselectively tri- and tetracyclic compounds of high molecular complexity. These results are in agreement with a mechanism in which the cyclopropanation precedes the rearrangement.

A new synthesis of (À)-(R)-muscone ((R)-1) by means of enantioselective protonation of a bicyclic ketone enolate as the key step (see 6 3 (S)-4 in Scheme 2) is presented. The C 15 macrocyclic system is obtained by ozonolysis (Scheme 7).

Dedicated to Professor Georg Frµter on the occasion of his 65th birthdayIn the 1990s, chemists from Firmenich [1a] reported the isolation of (À)-1 by chemical degradation of the labdane diterpene (+)-larixol.[1b] This unsaturated analogue of Ambrox [2] was named "Superambrox" as a result of its excellent odor qualities (Scheme 1).To our knowledge, the only synthetic approaches towards Superambrox are based on acid-mediated polyene cyclizations, [3] which afford the racemate with low stereoselectivity in only moderate yields. We now report a concise, highly selective synthesis of racemic Superambrox (AE )-1. The creation of the CÀC double bond in a highly substituted environment presents a special challenge, as this subunit is known to be prone to isomerization or skeletal rearrangement. A second difficulty lies in the stereoselective elaboration of the heterocycle.Our synthetic plan consists of the development of a new tandem type III intramolecular ene reaction/Oppenauer oxidation of dihydro-b-C14-aldehyde (2), a high-tonnage raw material, thus allowing a direct approach to the decalone 3, which has the properly positioned double bond. Acetoxylation from the less-hindered a face followed by intra-

Dedicated to Professor Georg Frµter on the occasion of his 65th birthdayIn the 1990s, chemists from Firmenich [1a] reported the isolation of (À)-1 by chemical degradation of the labdane diterpene (+)-larixol.[1b] This unsaturated analogue of Ambrox [2] was named "Superambrox" as a result of its excellent odor qualities (Scheme 1).To our knowledge, the only synthetic approaches towards Superambrox are based on acid-mediated polyene cyclizations, [3] which afford the racemate with low stereoselectivity in only moderate yields. We now report a concise, highly selective synthesis of racemic Superambrox (AE )-1. The creation of the CÀC double bond in a highly substituted environment presents a special challenge, as this subunit is known to be prone to isomerization or skeletal rearrangement. A second difficulty lies in the stereoselective elaboration of the heterocycle.Our synthetic plan consists of the development of a new tandem type III intramolecular ene reaction/Oppenauer oxidation of dihydro-b-C14-aldehyde (2), a high-tonnage raw material, thus allowing a direct approach to the decalone 3, which has the properly positioned double bond. Acetoxylation from the less-hindered a face followed by intra-