As 1,4-benzoquinonas são encontradas em toda a natureza, podendo ser sintetizadas por diversas estratégias. Esta revisão apresenta os desenvolvimentos recentes das metodologias de síntese, das reações de ciclo adição, da química computacional e dos estudos de pulso radiolítico. Destaca ainda a sua significância química e biológica e de seus compostos derivados.1,4-Benzoquinones are ubiquitous in nature and can be synthesized by diverse strategies. Recent developments on their synthetic methodologies, cycloaddition reactions, computational chemistry and pulse radiolytic studies are reported in this review. Their chemical and biological significance as well as their derivates' are also covered.

Syntheses of the piperolides, the fadyenolides, epoxypiperolide, and related compounds are described.( f ) -Narthogenin is also efficiently produced.From the Mexican plant Piper sanctum' we have previously isolated and characterised piperolide (l),' methylenedioxypiperolide (2),' ( + )-(7S,SS)-epoxypiperolide (3),'-" (-)-erythro-7,8-dihydro-7,8-dihydroxypiperolide (4),5 as well as a possible photoisomerisation product (5E)-piperolide (5),6*7 From Piper fudyenolii, indigenous to Jamaica, we have isolated and characterised similar butenolides, the fadyenolides (6) and (7).'These compounds are of particular interest for two reasons.First they are unique tetronates (derivatives of 4-hydroxybut-3-enolides) derived from higher plants rather than from fungal, microbial, or marine source^.^*^-'^ Secondly some of them, as well as certain of our synthetic products, have strong sedative as well as other most interesting physiological properties.It is tempting to speculate on a New World mutation in Piper species that leads from the usual pyrone derivatives such as kawain (8a)14 and methysticin (8b)14 produced by * We thank Dr. R. Pardasani for these experiments.

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A cyclic secondary α-amino acid, viz.

Synthetic and Antibacterial Studies of Rhodanine Derivatives with Indole-2,3-diones.-Six compounds of type (III) and the corresponding compounds of type (IV) are prepared and tested for their antibacterial activities. Compounds (IVb) and (IVc) show significant activities. -(PARDASANI, R. T.; PARDASANI, P.; SHERRY, D.; CHATURVEDI, V.; Indian J. Chem., Sect.

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Cycloaddition reactionsCycloaddition reactions O 0070 Theoretical and Synthetic Approach to Novel Spiroheterocycles Derived from Isatin Derivatives and L-Proline via 1,3-Dipolar Cycloaddition. -The reaction of the cyclic secondary α-amino acid (I) with isatin (II) via decarboxylative azomethine ylide formation and subsequent cycloaddition with dipolarophiles in moderate to good yields is described. Theoretical studies are performed to elucidate the stereochemistry of the products formed. -(PARDASANI*, R. T.; PARDASANI, P.; CHATURVEDI, V.; YADAV, S. K.; SAXENA, A.; SHARMA, I.; Heteroat. Chem. 14 (2003) 1, 36-41; Dep. Chem., Univ. Rajasthan, Jaipur 302 004, India; Eng.) -M. Schroeter 20-041

A facile synthesis of sprio{1‐aza‐bicyclo‐[3,3,0]‐6‐octene‐8,1′ ‐phenanthrene}‐2′‐ones has been accomplished by [3+2] cycloaddition of azomethine ylide (amy) generated from 9,10‐phenanthrenequinone and different secondary cyclic amino acids, namely, thiazolidine‐4‐carboxylic acid, L‐pyrrolidine‐2‐carboxylic acid (L‐proline), and piperidine‐2‐carboxylic acid (pipecolinic acid) with electron‐deficient dipolarophiles in 67%–79% yield. AM1 calculations have been performed to understand the stereochemical course of the cycloaddition. The products have been characterized by elemental analyses and spectroscopic techniques, namely IR, 1H NMR, and 13C NMR spectroscopies as well as mass spectrometry. Some of the synthesized cycloadducts showed moderate antioxidant activity. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:379–392, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20562