The insect moulting hormone crustecdysone has been isolated from the Australian brown pine, Podocarpus elatus R.Br., and detected in a number of other Podocarpus species from various parts of the world. A series of acetates and acetonides of crustecdysone has been prepared, and the mass and nuclear magnetic resonance spectra of these compounds analysed. A simple micro method of measuring the rate of acetylation of hydroxy groups in steroids has been developed to determine the steric environment of these groups.

Blumenols A, B, and C, new compounds from Podocarpus blumei, are shown to have structures (I), (2), and (3), respectively, with the opposite stereochemistry to that of abscisic acid (4) at the ring chiral centre. CHROMATOGRAPHY of the extract of the leaves of Podocarpus blumei Endl., afforded three new compounds, named blumenol A, B, and C, which showed strong U.V. absorption at 236 nm. Blumenol A, C13H2003 (microanalysis and M+ ion at m/e 224), m.p. 114-116', formed a monoacetate,

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12)We include all potential ion pairs. For example, glutamate-33, which has a lysine at 33 + 4 = 37 and another lysine at 33 -4 = 29, contributes two pairs of potential i.(i i 4) attractive pairs to the total number. The total obtained in the following paragraph for i.(i k 4) attractive pairs that involve glutamate was obtained on the same basis. (13) The factor of 2 is a bit too large. It only holds for an interior glutamate residue, Le., one that has a neighbor at both i -4and i + 4. Thus, only residue positions 5-280 would qualify.ABSTRACT: Monte Carlo simulations have been used to predict the molecular weight, molecular weight distribution, and composition of copolymers. The method is particularly suited to the simulation of copolymerizations carried out in the presence of chain-transfer agents (e.g., thiols). Calculations have been performed to show that selectivity shown in the initiation and termination reactions can have a dramatic influence on the composition and molecular weight distribution of cooligomers and copolymers.