C2-Symmetric enantiopure ethanotethered bis(alpha,beta-butenolides) as templates for asymmetric synthesis. Application to the synthesis of (+)-grandisol.
Starting from D-mannitol, we have prepared several C(2)-symmetric ethanotethered bis(alpha,beta-butenolides) and studied their [2+2] photocycloaddition reaction with ethylene. The protective groups of the central diol unit have a noticeable influence on the facial selectivity of the cycloaddition, the bis(trimethylsilyloxy) derivatives showing the highest diastereoselectivity. A theoretical conformational analysis of the substrates in the ground state is in good agreement with the diastereofacial selectivity experimentally observed. The bis(photocycloadducts) have been converted into the enantiopure cyclobutanes formally derived from the photoreaction of ethylene with gamma-hydroxymethyl-alpha,beta-butenolide, in which only a moderate facial selectivity had been previously found. As an application of these studies, we have developed a highly efficient and stereoselective synthesis of (+)-grandisol.
de March
Pedro
P
Departament de Química and Unitat de Cristal.lografia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Figueredo
Marta
M
Font
Josep
J
Raya
Javier
J
Alvarez-Larena
Angel
A
Piniella
Juan F
JF
D015107:4-Butyrolactone / Q000031:analogs & derivatives; D002384:Catalysis; D020650:Combinatorial Chemistry Techniques; D005663:Furans / Q000737:chemistry*; D007202:Indicators and Reagents; D008353:Mannitol / Q000737:chemistry*; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism; D013729:Terpenes / Q000138:chemical synthesis*
D005663:Furans; D007202:Indicators and Reagents; D013729:Terpenes; D008353:Mannitol; C004511:butenolide; C013009:grandisol; D015107:4-Butyrolactone