Experimental evidence for a [2 + 2] mechanism in the Lewis acid-promoted formation of α,β-unsaturated esters from ethoxyacetylene and aldehydes. Synthesis and characterisation of 4-ethoxyoxetes.
Verfahren zur Herstellung von die Pankreaslipase hemmenden Oxetanonäthylester der Formel
worin X Undecyl oder 2Z,5Z,Undecadienyl, C6 n-Hexyl, Y lsobutyl und Z Formyl, oder Y Carbamoylmethyl und Z Acetyl sind, durch Veresterung entsprechender Oxetanonäthanolen, durch Hydrierung der 3-Undecenylgruppe zur Undecyigruppe X in entsprechenden Ausgangsoxetanonäthylester oder durch N-Formylierung oder N--Acetylierung von entsprechenden primären Aminen.
Es werden neue die Pankreaslipase hemmende Oxetanone der Formel
worin Q, R¹ und R² die in der Beschreibung angegebene Bedeutung haben, offenbart, die ausgehend von entsprechenden β-Hydroxycarbonsäuren hergestellt werden.
The total synthesis of (-)-tetrahydrolipstatin utilizing two approaches is described. In the first, L-malic acid was used as a chiral template to obtain enantiomerically pure (R)-3-(benzyloxy)-tetradecanal (11) which was chain-extended using 1-(trimethylsilyl)-2-nonene and a Lewis acid. This advanced intermediate was further elaborated to the target compound in good overall yield. The second approach utilized lauraldehyde as a starting material and capitalizes on an asymmetric allylboronation (91 % ee). The product could be obtained enantiomerically pure by conversion to the (R)-acetoxymandelate ester and hydrolysis. Oxidative cleavage of the terminal double bond led to 11 which was further extended using 1,3- and 1,2-asymmetric induction based on existing neighboring chirality. The synthesis of tetrahydrolipstatin using the second approach comprises seven steps from 11 and proceeds in 38 % overall yield.
THE PREPARATION METHOD OF (3S,4S)-3-HEXYL-4-((R)-2-HYDROXYTRIDECYL)-OXETAN-2-ONE AND THE PRODUCT OF THAT METHOD