Excess volumes of binary mixtures of alcohols in methylcyclohexane have been determined at 30.0 and 40.0 "C, using a modified dilatometer of Brown and Smith. The systems include: (I) I-propanol -methylcyclohexane, (2) I-butanol -methylcyclohexane, (3) I-pentanolmethylcyclohexane, and (4) I-hexanol -methylcyclohexane. The VE values are found to be positive over the entire range of composition in all the four systems and the values are interpreted on the basis of the structure-breaking effect of methylcyclohexane.Les volumes d'exces des melanges binaires d'alcools dans le mtthylcyclohexane ont Ctt determines entre 30.0 et 40.0 "C en i~tilisant un dilatometre modifie de Brown et Smith. Ces systemes sont : (I) propanol-1 -mCthylcyclohexane, (2) butanol-1 -mCthylcyclohexane, (3) pentanol-1 -methylcyclohexane. (4) hexanol-1 -mtthylcyclohexane. O n a trouvC que ces valeurs VE sont positives dans tout le domaine de composition pour les quatresystemes et o n a interprCtC ces valeurs sur la base de I'effet de "bris de structure" du mCthylcyclohexane.[Traduit par le journal]Can. J. Chern., 52,788(1974)

Pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) are naturally occurring compounds isolated from various Streptomyces species. The PBDs exert their biological activity through covalent binding and exhibit cytotoxicity. Extensive studies have been carried out on the synthetic strategies of PBDs, and a sound understanding of structure activity relationships within this class of compounds has been developed. The PBDs have shown to interfere with the interaction of endonuclease enzymes of DNA and block the transcription by inhibiting RNA polymerase in a sequence specific manner. These processes have been thought to account for the biological activity of PBDs. The PBDs have also been used as a scaffold to attach different type of moieties leading to novel sequence selective DNA cleaving and cross-linking agents. The design and synthesis of C8-linked PBD dimers and other hybrids of PBDs has given a new insight towards the development of molecules with enhanced DNA binding affinity and sequence specificity compared to the naturally occurring PBDs. This improvement in the biological profile has been explained on the basis of certain factors like DNA cross-linking and doubling of DNA binding sites. There seems to be enough potential for further changing the substitution pattern and to design structurally modified PBDs by retaining the PBD core intact. In this review both the synthetic strategies and the structure-activity relationships, particularly the DNA binding and cytotoxicity studies of PBDs have been discussed.

A facile synthesis of bronchodilatory pyrrolo[2,1-b]quinazoline alkaloids by azidoreductive cyclization strategy employing TMSCl-NaI and bakers' yeast is described. Both the chemical and enzymatic methods are mild and take place at room temperature in good yields. Further, synthesis and resolution of vasicinone has been carried out by employing different lipases. It has been observed that lipase PS provides acetate of (S)-vasicinone in 98% ee.

Development of new chemotherapeutic drugs is the need of the hour to improve tuberculosis control, particularly in the developing world. In the last fourty years no new compound has been brought to the market for the treatment of tuberculosis. However, in recent years there is an enhanced activity in the research and development of new drugs for TB. Some compounds are presently in clinical development, while others are being investigated pre-clinically in an attempt to explore new molecules for the target based treatment of TB. Simultaneously some new targets are being identified and validated for their practical usefulness. Structures based on thiolactomycin could have considerable potential in the development of target based anti-TB agents. The present review provides an overview of the drugs that are being clinically used and the compounds that are in advanced stages of clinical as well as preclinical studies. We have also attempted to highlight the efforts that are being made in the development of new molecules based on thiolactomycin as lead compound, including studies from this laboratory.

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