Stereocontrolled total synthesis of (.+-.)-pentenomycins. I-III, their epimers, and dehydropentenomycin I

Abstract

Ab initio molecular orbital theory has been used to study in detail the C2H20 potential energy surface. Equilibrium structures and transition structures have been explicitly identified by using gradient techniques and the split-valence 4-31G basis set. Improved relative energies have been obtained by using the split-valence

The First Stereoselective Palladium-Catalyzed Cyclocarbonylation of β,γ-Substituted Allylic Alcohols

“…The following allylic alcohols are known compounds and have spectral data in accord with the literature data: 1a, 1b, 17 1d, 18 1f, 19 and 1i. 20 (E)-2,3-Diphenyl-2-propen-1-ol (1e). Colorless crystals, mp 68°C.…”

Secondary metabolites from species of the biocontrol agent Trichoderma

“…The same work also deduced that the major molecule with the R configuration coexists with its enantiomer in natural trichodenone A (71). Total synthesis of pentenomycins (Elliott et al 1983;Hetmanski et al 1984;Sugahara and Ogasawara 1999;Seepersaud and Al-Albed 2000;Gallos et al 2001), their racemates (Smith and Pilla 1980;Sono et al 1980;Smith et al 1982;Pohmakotr and Popuang 1991) and their analogues epipentenomycin II (79) and III (80) (Sono et al 1980;Elliott et al 1983) have been achieved.…”

Stereoselective synthesis of cis-decalins via Diels–Alder and double Michael addition of substituted Nazarov reagents

“…The dianions of phosphonate 9 a and the methyl-substituted phosphonate 96 were condensed with aldehyde 1 2 to give, respectively, a 77 and 44% yield of the trans olefinic products 13a and 13b as the only detectable isomers. Aldehyde 1 2 was prepared in a 72% yield via the alkylation of the lithium salt of l-trimethylsilylpropyne 1 4 with protected 3-bromo-1-tetrahydropyranyloxy-propane 15 followed by deprotection and k o 2 t -~u reported by Smith et al (12). The reaction of 18e with the zinc enolate of 19, followed by oxidation of the resulting P-/ hydroxy ester, gave P-keto ester 20e in a 62% yield for the two steps.…”

“…The aqueous phase was extracted several times with diethyl ether, the combined organic phase was washed with brine, dried, and evaporated in vacuo to give an yellow oil. Distillation (9S°C/3.5 Torr) afforded 14.70 g (92%) of l-brorno-3-tetrahydropyranyloxy-propane as a colorless oil; ir (cm-I): 3000-2800, 1475, 1370, 1150(s); 'H nrnr (6) (12) A solution of n-BuLi in hexanes (1.6 M, 8.4 mL, 13.5 rnmol) was placed in a 100 mL round bottom flask. The solvent was removed under vacuum at 20°C and 60 mL of anhydrous diethyl ether was added.…”