Molecular structure of Lantadene-B&C, triterpenoids ofantana camara, red variety: Lantadene-B, 22β-angeloyloxy-3-oxoolean-12-en-28-oic acid; Lantadene-C, 22 β-(S)-2′-methyl butanoyloxy-3-oxoolean-12-en-28-oic acid

(I)Lantadene-B: C35H52O5,M r =552.80, MonoclinicC2,a=25.65(1),b=6.819(9),c=18.75(1) Å,beta=100.61(9),V=3223(5) Å3,Z=4,D x =1.14 g cm–3 CuKagr (lambda=1.5418A),mgr=5.5 cm–1,F(000)=1208,R=0.118,wR=0.132 for 1527 observed reflections withF o ge2sgr(F o ). (II)Lantadene-C: C35H54O5·CH3OH,Mr=586.85, Monoclinic,P21,a=9.822(3),b=10.909(3),c=16.120(8)Å,beta=99.82(4),V=1702(1)Å3,Z=2,D x =1.145 g cm–3, MoKagr (lambda=0.7107Å), mgr=0.708 cm–1 F(000)=644,R=0.098, wR=0.094 for 1073 observed reflections. The rings A, B, C, D, and E aretrans, trans, trans, cis fused and are in chair, chair, sofa, half-chair, chair conformations, respectively, in both the structures. In the unit cell the molecules are stabilized by O-HctdotO hydrogen bonds in both the structures, however an additional C-HctdotO interaction is observed in the case of Lantadene-C.

Bridgehead substitution of 1-methoxybicyclo[2.2.2]oct 5-en-2-one derivatives: towards the synthesis of (±)-allo-cedrol [khusiol]1

Preparation of the key intermediates, 11 and 21, required for the synthesis of (+/-)-allo-cedrol (khusiol) is reported by a novel methodology involving the substitution at the bridgehead position of 1-methoxybicyclo[2.2.2]oct-5-en-2-one derivatives

Direct conversion of 13-beta-alkylgonatetraenes into 13-beta-alkylgon-4-en-3-ones

Birch reduction of 8,9-didehydroestradiol-17 beta 3-methyl ether 1 or 9(11)-didehydroestradiol-17 beta 3-methyl ether 2 followed by acid hydrolysis results in a mixture of 19-nortestosterone 8 and 19-nor-9 beta, 10 alpha-testosterone 9 in varying amounts. However, reduction of their acetates with sodium or lithium, tert-butyl alcohol in liquid ammonia and in the presence of aniline affords exclusively 19-nortestosterone. Similarly, 18a-homo-19-nortestosterone 12 is prepared from the acetate of 18a-homoestradiol-17 beta 3-methyl ether, 10.

Synthesis of chiral bicyclo[2.2.2]oct-5-en-2-ones via an intramolecular alkylation reaction

Generation of the thermodynamic dienolate of 9-bromocarvone derivatives 5, 7 and 11 furnished the chiral bicycle[2.2.2] octenones 6, 8 and 9 and 12 and 13 containing a bridgehead methyl group via an intramolecular alkylation reaction. In an analogous manner intramolecular alkylation reaction of the bromo enones 15a-e, obtained from carvone 2 by 1,3-alkylative enone transposition (-->14) followed by a regiospecific bromoetherification reaction, furnished the bicyclo[2.2.2]oct-5-en-2-ones 16a-e and 17a-e.

Isomerisation of 4-aryl-4-methylhex-5-en-2-ones to 5-aryl-4-methylhex-5-en-2-ones by an intramolecular ene-retro ene reaction sequence

Acid-catalysed thermal rearrangement of 4-aryl-4-methylhex-5-en-2-ones (products of the Claisen rearrangement of beta-methylcinnamyl alcohols and 2-methoxypropene) to isomeric 5-aryl-4-methylhex-5-en-2-ones via an intramolecular ene reaction of the enol tautomer followed by a retro ene reaction of the resultant acetylcyclopropane is described. Formation of the known diketone 13 via the ozonolysis of the rearrangement product 10, confirmed the structures of the rearranged enones, whereas formation of the enone 15 containing an extra methyl group on the styrene double bond confirmed the proposed mechanism. Finally, the rearrangement has been extended to the formal synthesis of beta-cuparenone 20 via the enones 22 and 23.

Spiroannulation of a cyclopentane ring. Synthesis of spiro[4.n](n+5)alk-2-en-1-ones

A methodology based on Claisen rearrangement-Wacker oxidation and intramolecular aldol condensation strategy starting from cyclic ketones leading to spiro[4.n](n+5)alk-2-en-1-ones has been developed. Thus one-pot Claisen rearrangement of the alkyl alcohols 6a-c furnished the aldehydes 8a-c, which on regiospecific oxidation using Wacker conditions generated the keto-aldehydes 9a-c. Finally, intramolecular aldol condensation transformed the keto-aldehydes 9a-c into spiroannulated products 10a-c.

A comparison of the DNMR behaviour of methyl 5,6-bis(2-methoxyphenyl)-1,4-dimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-endo-carboxylate and its 7-oxa analogue

Methyl 5,6-Bis(2-methoxyphenyt)-1,4-dimethyl-7-oxobicyclo[2.2.1]hept-5-en-2-endo-carboxylate, a moderately crowded norbornenone ester, exhibits complex VT-DNMR behaviour. A similar behaviour is not seen in its 7-oxa analogue, showing that conformational transmission from position 7 has a crucial influence on the distance parameters that govern the dynamic processes involving the substituents on the bicycloheptene framework.

(2E)-1-(5-Chlorothiophen-2-yl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one

In the title molecule, C(16)H(15)ClO(4)S, the chlorothiophene and trimethoxyphenyl rings make a dihedral angle of 31.12 (5)degrees. The C = C double bond exhibits an E conformation. In the crystal, C-H center dot center dot center dot O interactions generate bifurcated bonds, linking the molecules into chains along the b axis.

Explorations en route to synthesis of tashironins: singlet oxygen cycloaddition to 1,3-cyclopentadienes embedded within allo-cedrane framework

In an approach directed toward a tashironin based complex natural product, efficacy of the singlet oxygen mediated [4+2]-cycloaddition to a tetracyclic cyclopentadiene has been evaluated to install the key cis-1,4-dihydroxy functionality. (C) 2011 Elsevier Ltd. All rights reserved.

(2E)-1-(5-Chlorothiophen-2-yl)-3-(2,3-dimethoxyphenyl)prop-2-en-1-one

In the title compound, C(15)H(13)ClO(3)S, the chlorothiophene and dimethoxyphenyl groups are linked by a prop-2-en-1-one group. The C=C double bond exhibits an E conformation. The molecule is non-planar, with a dihedral angle of 31.12 (5)degrees between the chlorothiophene and dimethoxyphenyl rings. The methoxy group at position 3 is coplanar with the benzene ring to which it is attached, with a C-O-C-C torsion angle of -3.8 (3)degrees. The methoxy group attached at position 2 of the benzene ring is in a (+)synclinal conformation, as indicated by the C-O-C-C torsion angle of -73.6 (2)degrees. In the crystal, two different C-H center dot center dot center dot O intermolecular interactions generate chains of molecules extending along the b axis.

Synthesis, growth, and characterization of a new NLO material 3-(2,3-dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one

3-(2,3-Dimethoxyphenyl)-1-(pyridin-2-yl)prop-2-en-1-one (DMPP) a potential second harmonic generating (SHG) has been synthesized and grown as a single crystal by the slow evaporation technique at ambient temperature. The structure determination of the grown crystal was done by single crystal X-ray diffraction study. DMPP crystallizes with orthorhombic system with cell parameters a = 20.3106(8)angstrom, b = 4.9574(2)angstrom, c = 13.4863(5)angstrom, alpha = 90 degrees, beta = 90 degrees, gamma = 90 degrees and space group Pca2(1). The crystals were characterized by FT-IR, thermal analysis, UV-vis-NIR spectroscopy and SHG measurements. Various functional groups present in DMPP were ascertained by FTIR analysis. DMPP is thermally stable up to 80 degrees C and optically transparent in the visible region. The crystal exhibits SHG efficiency comparable to that of KDP. (C) 2011 Elsevier B.V. All rights reserved.

En Masse relay selection algorithms for multi-source, multi-relay, decode-and-forward cooperative systems

Opportunistic relay selection in a multiple source-destination (MSD) cooperative system requires quickly allocating to each source-destination (SD) pair a suitable relay based on channel gains. Since the channel knowledge is available only locally at a relay and not globally, efficient relay selection algorithms are needed. For an MSD system, in which the SD pairs communicate in a time-orthogonal manner with the help of decode-and-forward relays, we propose three novel relay selection algorithms, namely, contention-free en masse assignment (CFEA), contention-based en masse assignment (CBEA), and a hybrid algorithm that combines the best features of CFEA and CBEA. En masse assignment exploits the fact that a relay can often aid not one but multiple SD pairs, and, therefore, can be assigned to multiple SD pairs. This drastically reduces the average time required to allocate an SD pair when compared to allocating the SD pairs one by one. We show that the algorithms are much faster than other selection schemes proposed in the literature and yield significantly higher net system throughputs. Interestingly, CFEA is as effective as CBEA over a wider range of system parameters than in single SD pair systems.