The 0.r.d. curves of ca. 40 carotenoids have been measured, chiefly in dioxan, over the range 400-200 nm. The chromophore in all cases is a conjugated polyene system which is perturbed by one or two chiral end-groups.The curves are analysed in terms of the simple additivity of the effects of end-groups, and the absolute configurations of several compounds have been provisionally assigned.MANY carotenoids contain one or more asymmetric carbon atoms, but little information is available concerning the absolute or relative configurations of these centres. Capsanthin (1) has been degraded to the acid (2) which on further oxidation, gave (-)-camphoronic acid (3),2 also obtained from (+)-camphor (4) of known 3 absolute configuration. Since the two oxygen functions This paper is Part LXII in the Westfield College series on optical rotatory dispersion, preceding paper, Part LXI, G.

The c.d. curves of seventeen pyrrolizidine alkaloids have been measured, together with curves for the component parts of these alkaloids, viz pyrrolizidine bases and necic acids. The curves are discussed in relation to the nature and relative positions of the chromophores, first for the component acids and bases and then for the macrocylic alkaloids. Some c.d. curves have been measured a t low temperatures as well as at room temperature; some 0.r.d. curves have also been measured.

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Chiral alcohols give significant Cotton effects absorption maximum above 200 nm, and consequently aliphatic alcohols have been used extensively as solvents for the study of 0.r.d. and c.d. In addition, it has been possible to disregard the presence of hydroxy substituents in work with compounds containing other chromophores between 185 and 198 nm. COMPOUNDS containing hydroxy groups as the only substituent on a saturated hydrocarbon skeleton, show no

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