Circular dichroism of 1,3-dithiolans

Abstract

The circular dichroisrn of a range of 1,3-dithiolans, mainly in the steroid series, generally consists of two maxima of opposite sign a t about 270 and 245 nm., with the latter more intense.spectra of 1,3-dithiolans exhibit a weak band at about 245 nm. (E -350) corresponding to the n+a* transitions of the sulphur atoms. In the circular dichroism spectra (in methanol,, dioxan,, or, in the present work, cyclohexane 3, two oppositely signed absorptions are generally seen, one between 260 and 280 nm., and the other, which is always more intense, between 240 and 250 nm. To understand the spectra it is necessary to examine carefully the shape and symmetry of the dithiolan chromophore. N.m.r. spectra of 2-substituted 1,3-dioxolans show that the ring undergoes pseudorotation between the envelope and the two enantiomeric half-chair conformations, but even with very bulky groups, e.g., t-butyl, no preference for the envelope form (which would tend to minimise 1,3interactions) could be detected. Therefore, although a " time-average conformation " of a molecule exhibiting pseudorotation is not necessarily the same as the " average conformation," the 1,3-dioxolan ring (and, by extension, the 1,3-dithiolan ring) appears to be planar. The planar dithiolan chromophore (Figure 1) c\ I /D HzC--!-CHI 4 F. Alderweireldt and M. Anteunis, Bztll. SOC. chim. belges,

Synthesis and Biological Evaluation of Pentacycloundecylamines and Triquinylamines as Voltage‐Gated Calcium Channel Blockers

“…The physical characterization, data not presented, correlated with the physical characteristics described by Cooksen et al [17]. …”

“…The pentacycloundecylamine 7a served as a lead compound and R substitution was guided by structure–activity relationship (SAR) data from previous studies [16]. In short, pentacyclo-[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane-8,11-dione ( 4 ), also called Cookson’s “cage” compound, was synthesized by photochemically initiated intramolecular [2+2] cycloaddition of the Diels–Alder adduct ( 3 ) obtained from the reaction of 1,3-cyclopentadiene ( 2 ) with p -benzoquinone ( 1 ) [17]. The synthesis of the oxa-pentacycloundecylamine derivatives ( 7a – e ), illustrated in Scheme 1, has been described previously by our group [16c, 18].…”

“…The pentacyclo[5.4.0.0 2,6 .0 3,10 .0 5,9 ]undecane‐8,11‐dione ( 4 ) was synthesized according to the well‐established method previously described . The physical characterization, data not presented, correlated with the physical characteristics described by Cooksen et al .…”

Structure-Activity Relationships of Polycyclic Aromatic Amines with Calcium Channel Blocking Activity

“…C, H and N analyses were all within acceptable limits (± 0.4%). (1) ]undecane-8,11-dione (5 g, prepared according to the method of Cookson et al [19,20] ) was dissolved in tetrahydrofuran (THF, 50 ml) and cooled to ±5 °C in ice. An equimolar quantity of the desired amine was slowly added under stirring.…”

Biphasic Photochemistry: The First Actinometric Reaction on a Solid Support

“…ometer are: Upon examining the literature, the reaction 3-4 (Cookson, 1958(Cookson, , 1964 seemed to be a possible candidate. Unfortunately compound 3, which met all requirements for a solution actinometer, revealed poor stability o n silica gel, giving the enolization product 5 in variable yields depending on the degree of hydration of the silica.…”