No abstract

A macrocyclization–transannulation strategy is the crux of an efficient total synthesis of the benzolactone enamide apicularen A (see scheme; Bn=benzyl). Key steps include a four‐component coupling, a Stille cross‐coupling to introduce the aromatic moiety, and the formation of the enamide from a hemiaminal. The size‐selective macrolactonization of the ethoxyvinyl ester shown was followed by transannular etherification in excellent yield.

The paper illustrates two efficient routes to macrolactone 19 containing a 3-(para-methoxybenzyloxy)propyl side chain at C-15. The chiral center at C-15 was introduced by a Noyori reduction of keto ester 5. The intermediate common to both routes, aldehyde 8, was prepared from keto ester 5. The subsequent chain extension utilized Evans aldol reactions. The first route leads to the alkene 14, which was used, after hydroboration, for a Suzuki cross-coupling reaction with vinyl iodide 15. The derived seco acid 18 was converted into the macrolactone 19 by a Mitsunobu lactonization by using immobilized triphenylphosphine. Alternatively, an aldol reaction of 8 with the 4-pentenoyl derivative 20 was used to prepare alkene 26. This building block led to ester 28, which could also be converted into macrolactone 19 by the classical ring-closing metathesis. After conversion of the C-15 side chain to the corresponding aldehyde, the enamide was introduced through hemiaminal formation and formal elimination of water. Separation of the double-bond isomers and removal of the silyl protecting groups provided salicylihalamides A (E)-1 and B (Z)-1.

The tricyclic 6-7-6 core structure of the triterpene salvadione (1) was obtained in an efficient manner from the aryl bromide 16 and the alkyl iodide 35 carrying a methylenecyclohexane group at the terminus. Alkylation of the anion derived from 16 with the iodide 35 gave the tethered system 36. This compound was converted into the allylic bromide 40. Finally, a

The new monodentate phosphoramidites 8a−g and bidentate phospholanes 13a−e are prepared in an ex-chiral-pool synthesis from D-mannitol. Chiral diols 7a−g, obtained via nucleophilic ring opening of bis(epoxides) 6a−b, are the key intermediates for the production of both classes of ligands. Treatment of 8a−g or 13a−e with [PdCl 2 (COD)] or [Rh(COD) 2 ][-SO 3 CF 3 ] yield the corresponding Pd (10a, 10f, 15a) and Rh compounds (9a−g and 14a−e), respectively. The C 2 symmetry of the complexes in the solid state is demonstrated by X-ray structure investigations performed on 10a, 10f and 15a. Sur-