Versuche zur Totalsynthese von Brefeldin A

Preliminary results leading towards the total synthesis of Brefeldin A are presented.     

Γ-Lakton-cis-anellierung an Δ2- und Δ3- Cholesten

γ-Lactone-cis-annulation to Δ²- and Δ³- Cholestene. From Δ²- and Δ³- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The ¹³C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported.     

Zur Elektronenstruktur metallorganischer Komplexe der f‐Elemente. 64 Äußert sich die zwitterionische Natur des Triphenylphosphanoxid‐Liganden auch in seinen spektrochemischen Eigenschaften?

Electronic Structures of Organometallic Compounds of f Elements. 64 Does the Zwitterionic Nature of the Triphenylphosphine Oxide Ligand Manifest itself in its Spectrochemical Properties? The triphenylphosphine oxide mono adducts of the moiety tris(η⁵‐cyclopentadienyl)lanthanide(III) (Ln(Cp)₃; Ln = Pr ( 1 ), La ( 2 )) were synthesized and structurally characterized. The Ln–O distances of these compounds are noticeably shorter than those of the corresponding THF adducts. A crystal field (CF) analysis of the optical spectra of 1 leads to a low absolute value of the quadratic CF parameter which is comparable with those of [Pr(Cp)₃(L)]^? adducts with anionic bases but not with [Pr(Cp)₃(MeTHF)]. Reasons for the latter finding are presented.