A General, Asymmetric, and Noniterative Synthesis of Trideoxypropionates. Straightforward Syntheses of the Pheromones (+)-Vittatalactone and (+)-Norvittatalactone

Abstract

A novel, highly stereocontrolled, and very flexible synthetic access to biologically relevant trideoxypropionate building blocks in optically pure form has been developed. On the basis of a three-step sequence comprising a thermal oxy-Cope rearrangement, an iridium-catalyzed hydrogenation, and an auxiliary-controlled enolate methylation, trideoxypropionates with easily adjustable relative configuration were synthesized in excellent yields. In addition, the functionalized end groups allow for chemoselective manipulations and further elongation of the chain. The underlying strategy constitutes the first noniterative process for the assembly of polydeoxypropionates and has further been applied in total syntheses of the pheromones (+)-vittatalactone and (+)-norvittatalactone, which had been isolated from the striped cucumber beetle Acalymma vittatum.

Asymmetric Hydrogenation of Olefins Using Chiral Crabtree-type Catalysts: Scope and Limitations

“…[115][116] However, Ir-PHOX catalysts ( Figure 3) were efficient in the diastereoselective hydrogenation of the enol carbamate S43, analogue to enol ester S42, for which several Rh/P catalysts failed. 113 As with enol ester S42, the use of the bulky PHOX ligand 5c (Figure 3) and its enantiomer (ent-5c) afforded both diastereoisomers in high yields and diastereomeric ratios (Scheme 14). …”

“…The best activities and selectivities were achieved using ligand 5c containing bulky mesityl groups at the phosphine moiety (Figure 3). 113 Enol benzoate S42 was hydrogenated to the anti product in 99% yield and 96:4 dr, whereas the epimeric syn product was achieved in 98% yield and 97:3 dr using the enantiometic 5c ligand (Scheme 14, step (a)). The hydrogenated products were used to prepare biologically relevant trideoxypropionate building blocks in the optically pure form by a simple auxiliary-controlled enolate methylation (Scheme 14, step (b)).…”

Structure elucidation of female-specific volatiles released by the parasitoid wasp Trichogramma turkestanica (Hymenoptera: Trichogrammatidae)

“…Since the preparation of enantiomerically pure syn , syn -2,4,6-trimethylnonanal has been described [25–28], our approach includes a formal synthesis of optically active A and B . Until now, we did not find suitable conditions to separate the enantiomers of the tetramethyldiene 22 and the respective allyl alcohol 23 (or corresponding derivatives thereof) in order to assign the absolute configuration of the natural products by enantioselective gas chromatography.…”

Eine konvergente und stereoselektive Synthese der Glycolipidkomponenten Phthioceransäure und Hydroxyphthioceransäure

“…[8] blen Aufbau von Trideoxypropionaten 6 basiert (Schema 2). [10] Durch eine dreistufige und leicht skalierbare Sequenz aus Oxy-Cope-Umlagerung, Hydrierung und Enolatmethylierung erhielten wir Zugang zu Synthesebausteinen des Typs 6 in hoher Gesamtausbeute und Stereoselektivität direkt aus den Aldolprodukten 5.…”

“…Unser Syntheseplan für die Hydroxyphthioceransäure (3) sah vor, ihre Struktur konvergent aus drei Bausteinen (8)(9)(10) ähnlicher Grçße und Komplexität aufzubauen und diese durch Kreuzkupplungsreaktionen und nachfolgende stereoselektive Hydrierungen zum vollständigen Kohlenstoffgerüst von 3 zu verknüpfen (Schema 3). Sowohl 8 als auch 10 sollten sich jeweils in wenigen Schritten aus dem Trideoxypropionat 6 synthetisieren lassen.…”