Circular dichroism (CD) is used to give information about the chirality or handedness of molecular systems. It is particularly widely applied to determine the secondary structure of proteins such as biopharmaceutical products.

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The synthesis of ( -) -trans-8-methylhydrindan-5-one (X) and of ( +) -trans-8-methylhydrindane-2,5-dione (VIII) from an intermediate (I) of known absolute configuration is described. Rotatory dispersion measurements indicate that no major conformational distortion is produced in the cyclohexanone ring by the trans fusion with a cyclopentane ring. The bearing of this observation on the stereochemistry of B-norcholestanone (XIII) is discussed and the rotatory dispersion curves of a pair of cis-and trans-4-keto-hydrindanes is also reproduced. The rotatory dispersion curve of (+)-trans-8methylhydrindane-2,5-dione (VIII) represents the summation of the two individual chromophores acting independently without vicinal interaction.The most important reason for the rapid extension of the rotatory dispersion technique4 to a variety of organic molecules has been the conclusion that the majority of the results derived from a study of steroidal and other polycyclic ketones5of known stereochemistry and rigid conformationcould in fact be ascribed largely to the immediate bicyclic environment around the carbonyl chromophore. This postulate was established by syn-thesizing6r7 a number of optically active decalones, octalones and hydrindanones of known absolute configuration and comparing the shapes of their rotatory dispersion curves with that of steroid standards. The sensitivity of the rotatory dispersion curve of a given cyclic ketone to stereochemical alterations was first established in the steroid seriesg and the characteristic shape ascribed to 5a-(A/B trans) and 5P-(A/B cis) 3-ketosteroids was also found' in the transand cis-decalone series. It was of considerable interest, therefore, to determine whether this observation would also hold true when the size of the adjacent ring is altered and, for reasons outlined below under "Rotatory Dispersion Results," the key substance required for this study was the previously unknown, optically-active trans-8-methyl-5-hydrindanone (X) .Synthetic Studies.-Since it was indispensable that the absolute configuration of our final product be known, it was decided to start with (+)-trans-2-ket0-1O-methyl-A~~~-hexahydronaphthalene (I)l0 whose absolute configuration1' was established be- (1958).Chemical Cg., St. Louis, Mo.) for a generous gift of a precursor of I.(11) Throughout the present paper all structural formulas are intended to depict absolute configurations using the standard steroid notation.cause of the transformation12 of its ( -)-antipodeI3 into a natural steroid. Reduction of I with lithium in liquid ammonia14 provided ( +)-trans-A6-10methyl-2-octalone (11) accompanied by some of the alcohol IIIa and a small amount of a high melting dimer, which on the basis of its spectral and optical rotatory dispersion properties is assigned tentatively structure IV. Further reduction of the octalone I1 with lithium aluminum hydride furnished trans-A6-10-methyl-2-octalol (IIIa), which also could be obtained in one step by sodiumethanol treatment of the parent ketone I. The alcohol IIIa repre...

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