Spiro, defined

Research conducted by Simons using antiglucocorticoids, including compounds which covalentiy bind to the GR (124), eg, dexamethasone 21-mesylate, has better defined the stmcture and function of the GR. Spiro C-17 oxetanes have shown potent antiglucocorticoid activity in whole cell systems (125,126). 

Inter [4+2]/intra [3+2] This typeof tandem reaction nsmg nitroalkenes hasbeen expbred most extensively Four subfamilies of tandem cycloaddiQon exist, which anse from the font different pomts of attachment of the dipolarophihc tether They are defined as fused, spiro, and bridged modes, as depicted m Scheme 8 37... 

When comparing these results with those previously obtained using carbohydrate-based vinyl ethers as chiral dienophiles, this improved facial diastereoselectivity to heterodienes under similar conditions is noteworthy.81 The efficient chiral transfer in the second example might mostly be attributed to the specific architecture of the l,2 5,6-di-0-isopropylidene-a-D-glucofuranose moiety.Those findings open the way to develop well-defined spiro-carbohydrate templates towards improved auxiliaries for chirality transfer in a wide range of syntheses. 

Two other well defined carboranes 55g and 76 (vide infra, Section 3.2.7) are present in the reaction mixture containing 64c (vide infra, Scheme 3.2-35). Although pure 55g could not be isolated, its solution-state structure follows from a complete set of NMR spectra [71b], This unusual carborane is a spiro derivative without precedence and belongs to the family of 2,3,5-tricarba-mdo-hexaboranes(7). Ab initio MO calculations and NMR data indicate that the boron atom linked to the C3B3-framework by an endohedral C-B bond takes part in the cluster bonding [71b] (similar to an endohedral C-H bond in the other carboranes 55). 

The naphthopyran ring-opening reactions have not been as well studied as they have for the spiropyrans and spiro-oxazines. Aubard et al. [75] recently reported that in acetonitrile and hexane, irradiation of CHRl resulted in a broad transient spectrum after 0.8 psec, having three maxima at 360-370 nm, 500 nm, and 650 nm. At 1.8 psec, a well-defined band forms at 425 nm. From 10 to 100 psec, there is little further evolution except for a continued growth in the peak at 425 nm of about 15%. There is also a decrease in the overall bandwidth. The mechanism in Scheme 9 has been proposed, where B2 and B, are isomers of the mero-form. Three isobestic points were identified in the transient spectra at different times, suggesting four transient states. Forming between 0.8 and 1.6 psec, the Bi state was assigned as the cis isomer. This had a spectrum similar to that obtained for Tamai s X transient of the spiro-oxazine NOSH, which was obtained at subpicosecond time scales [26]. 

Structure-based and source-based nomenclature rules have been extended to regular double-strand (ladder and spiro) organic polymers [7]. A double-strand polymer is defined as a polymer the molecules of which are formed by an uninterrupted sequence of rings with adjacent rings having one atom in common (spiro polymer) or two or more atoms in common (ladder polymer). 

An extension of this reaction principle to other complexes related to 41 and other dienes is limited. However, 1,3-cyclopentadiene (lh) or 1,3,5,7-cyclooc-tatetraene substitute the tj6-1,3,5-cycloheptatriene ligand, and [Cr(CO)2(tj5-C5H5)(t/3-C5H7)] (5) and [Cr(CO)3(t/6-CgH8)] (72), are formed, respectively, in high yield (73). In order to prevent the formation of 5, spiro[4.2]hepta-1,3-diene and spiro [4.4] nona-1,3-diene (lu) (74) were used instead of lh. The diene lu should not readily form derivatives of t]5-cyclopentadienyl ligands. While spiro [4.2] hepta-1,3-diene does not form well-defined products, lu adds to 41 in a smooth reaction (73) [Eq. (22)]. The constitution of 43 was... 

Anyhow, no ANSA structure (as defined by Becke-Goehring 26 ) was ever observed in our works and we could conclude that the SPIRO and BINO configurations do exist in final products of the reaction of N3P3C16 with diamines and polyamines. 

The reaction of N3P,C16 with natural polyamines as tumor finders leads then stereo-selectively and regioselectively to well-defined specific configurations, mainly SPIRO, ANSA, BINO, DISPIRO, TRISPIRO, SPIRO-ANSA, SPIRO-BINO, DISPIRO-BINO, DISPIRO-DIANSA-BINO. 

Figure 9 Variations of Na/Cl, Br/Cl, and values during evaporation of seawater. Degree of evaporation is defined as the ratio of Br in the solution at different stages of evaporation to the initial Br in seawater (sources McCaffrey et al., 1987 Raab and Spiro, 1991 Vengosh et al., 1992).

For geometrically rather well defined situations for the application of the antioctant rule two basic situations are differentiated, namely condensed systems (fused rings) XXV and spiro-compounds XX VI. The geometrical arrangements in these systems can be defined... 

Upon irradiation with UV light the colourless spiro compounds transform into their highly collared merocyanine forms (Scheme 11). The colour of the merocyanine form is highly dependent on the solvent polarity and an Esp scale was defined similar to the Et(30) scale ... 

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