An Investigation of the Diastereoselectivity of Nucleophilic Additions to 6-Methyl-1-oxa-4-thiaspiro[4.5]dec-6-ene-7-carbaldehyde. Hybridization of the Nucleophile Alters the Diastereoselectivity

Synthesis of highly functionalized 2-thiaspiro[4.5]deca-6,8-dienes via atom efficient tandem Michael addition/Thorpe–Ziegler cyclization

The reaction of 2,4-bis((Z)-arylidene)dihydrothiophen-3(2H)-ones and 2-(1-arylethylidene)malononitriles proceeded through a tandem sequence of reactions in a single step affording 2-thiaspiro[4.5]deca-6,8-dienes in quantitative yields.

Towards synthetic adrenaline receptors--shape-selective adrenaline recognition in water

In spite of their key role in signal transduction, the mechanism of action of adrenergic receptors is still poorly understood. We have imitated the postulated binding pattern of the large membrane protein with a small, rationally designed synthetic host molecule. Experimental evidence is presented for the simultaneous operation of electrostatic attraction, hydrogen bonds, pi stacking, and hydrophobic interactions. By virtue of this combination of weak attractive forces, adrenaline derivatives in water are bound with high shape selectivity for the slim dopamine skeleton. We think that these findings support the postulated cooperative interplay of noncovalent interactions in the natural receptors. In addition, they provide access to a new type of adrenaline sensor. This may be the first step towards an artificial signal-transduction system.

Heteroatom influence on the pi-facial selectivity of Diels-Alder cycloadditions to 1-oxa-4-thia-6-vinylspiro[4.5]dec-6-ene, 3-methoxy-3-methyl-2-vinylcyclohexene, and 3-methoxy-2-vinylcyclohexene

The facial selectivities of the Diels-Alder cycloadditions of several dienophiles to the title substrates were studied. The observed selectivities are interpreted as a consequence of the relative steric interactions offered by the substituents. The addition of dimethylacetylene dicarboxylate (DMAD) is influenced by the electrostatic repulsion arising from the interaction of an electron pair orbital on the acetal oxygen and the orthogonal pi-orbital of the acetylene unit in DMAD in the syn-to-oxygen addition of the latter. This repulsion is offset on coordination of Li+ to the said oxygen electron pair orbital, and the addition thus proceeds syn to oxygen. The enhanced and accelerated syn-to-oxygen addition in lithium perchlorate in nitromethane is interpreted as a consequence of the coordination of Li+ to both the acetal oxygen and a heteroatom in the dienophile that brings them in close proximity to facilitate a reaction. The Li+-oxygen combination, however, also exerts some steric effect that results in reduced syn-to-oxygen addition of dienophiles having large substituents such as N-phenylmaleimide.