Visible light sensitive cyclomer and its tautomeric dispiro compound formed from bispyridinyl diradical

Two-electron reduction of 4,4'-(1,5-pentanediyl)bis(N-methylpyridinium) (52+) with sodium amalgam in degassed acetonitrile leads quantitatively to the formation of a cyclomer of 3,15-dimethyl-3,15-diazatricyclo[10.3.1.12,6]heptadeca-4,6(16),12(17),13-tetraene (6) by intramolecular cyclization. In degassed acetonitrile, 6 is stable for a long time at room temperature and, hence, a highly stable species. In contrast, 6 undergoes a photochemical reaction to give its valence tautomer having a dispiro structure, 3,10-dimethyl-3,10-diazadispiro[5.0.5.5]heptadeca-1,4,8,11-tetraene (7), when irradiated with visible light shorter than 450 nm. Noteworthy is the experimental fact that 7 is unstable to heat and, hence, reverts back to 6 by application of heat.     

On the Numbers of Orbits of Permutations under an Operator Related to Eulerian Numbers

In two previous papers an operator on permutations was introduced and its applications to Eulerian numbers were discussed by means of periods and orbits under the operator. In this paper, observing particular subsequences of permutations, an explicit formula for the number of orbits is given for each period. Several identities concerning the number of orbits and its related numbers are also derived.AMS Subject Classification: 05A05, 05A10.     

New humulane-type sesquiterpenes from the liverworts Tylimanthus tenellus and Marchantia emarginata subsp. tosana

The ether extract of the New Zealand liverwort Tylimanthus tenellus produced three new sesquiterpenes, together with (+)-3,11-eudesmadiene and (-)-4(15),11-eudesmadiene which were enantiomeric to those isolated from higher plants. The structures of the new sesquiterpenes were established by 2D NMR spectral data and/or X-ray crystallographic analysis. Those structures were shown to be humulane type sesquiterpene alcohol, and its esters of 2,4-hexadienedioic acid 3,4-dihydroxy-2,5-diphenyl-gamma-lactone. 1,6-Humuladien-10-ol was also isolated from Japanese liverwort Marchantia emarginata subsp. tosana. The absolute configuration of 1,6-humuladien-10-ol was determined by (1)H-NMR resolution of its diastereomeric methoxy-alpha-trifluoromethylphenylacetyl (MTPA) esters. It was shown to be (3S,10R)-1,6-humuladien-10-ol.     

A new abietane and two dimeric abietane diterpenes from the black heartwood of Cryptomeria japonica

Three new diterpenes, sugikurojins A-C (1-3) were isolated from the black heartwood of Cryptomeria japonica. The structure of sugikurojin A was deduced to be 19-hydroxy-6,7-dehydroferruginol on the basis of extensive NMR experiments. Sugikurojin B was a dimer of 6,7-dihydroxyferruginol and 6,7-dehydroferruginol with a 6-O-11' linkage. Sugikurojin C was a dimeric ferruginol with 6-O-7' and 7-O-6' linkages. Also obtained in this investigation were the known compounds formosaninol (4), 15 sesquiterpenes (5-19), 16 diterpenes (20-35), three phenylpropanoids (36-38), and a phenolic compound (39).     

Dramatic effects of boryl substituents on thermal ring-closing reaction of vinylallenes

The unidirectional thermal ring-closing reaction of cis-4-phenyl-5-borylpenta-1,2,4-triene giving 4-boryl-3-methylene-1-phenylcyclobutene proceeded significantly faster than that of the trans-isomer. The large rate difference between the cis- and trans-stereoisomers is ascribed to electronic participation of the vacant boron p orbital in the transition state SHOMO.