Visible-light-transparent p-type NiO films were deposited by reactive RF sputtering under unintentional heating. An optical transmittance of >80% was obtained in the wavelength range of 500–800 nm when the films were deposited under a very low O2 fraction in the gas phase O2/(Ar+ O2) = 0.5%. This result may reflect a decrease in the concentration of Ni vacancies due to the increase in their formation energy under oxygen-poor deposition conditions. Heterostructure pn junctions consisting of p-type NiO and n-type ZnO layers were also deposited. We eventually observed a slight but noticeable photovoltaic effect.

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The Zoanthus alkaloids, to which zoanthamines and (À)-norzoanthamine (1) belong, have attracted a great deal of attention in the synthetic community owing to their significant biological activity [1] as well as their unique and complex heptacyclic structure. Although several groups have attempted the synthesis of these alkaloids, [2][3][4] only the Miyashita research group has accomplished a total synthesis. [4] The most challenging steps towards the total synthesis of (À)-norzoanthamine are the construction of the bisaminal skeleton in the CDEFG ring moiety and a stereocontrolled construction of the densely functionalized C ring, which contains four quaternary chiral centers. During the course of our studies, we have already developed an excellent methodology for bisaminal formation (Scheme 1), [3] and have reported a synthesis of the ABC ring moiety in the preceding paper.[5] Herein, we report the total synthesis of (À)-norzoanthamine from the key intermediate 8.Our synthetic strategy for the preparation of 1, starting from 8, is shown in Scheme 2. (À)-Norzoanthamine could be synthesized from a ketoacid 4 or its equivalent based on our efficient method of bisaminal formation. The cyclization precursor 4, in turn, could be derived from the aldehyde 5 by the Horner-Emmons reaction with nitrogen-containing ketophosphonate 6, which can be prepared from lactone 9.[6] As mentioned in the preceding paper, we envisioned that the cyclopentanol moiety in tetracyclic 8 might serve as a handle for introducing the remaining C1-C7 fragment. Thus, oxidative cleavage of cyclopentanone 7 and subsequent functional group transformation would provide the requisite aldehyde 5. For these manipulations, the key intermediate 8 was first converted into cyclopentanone 7, in which the a,b-unsaturated cyclohexenone moiety in ring A is masked as cyclohexanol after introducing the methyl group at C26. Synthesis of aldehyde 5, a substrate for the HornerEmmons reaction, was commenced with 1,4-addition of enone 8 for introducing the methyl group at C26 (Scheme 3). Treatment of enone 8 with Gilman reagent led to the corresponding ketone in 91 % yield, which was then Scheme 1. Model study of bisaminal formation. Boc = tert-butoxycarbonyl.Scheme 2. Retrosynthetic analysis. MOM = methoxymethyl, TBDPS = tert-butyldiphenylsilyl, TBS = tert-butyldimethylsilyl.

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Only eight steps were required for the total synthesis of (+)‐citreoviral (3) from chiral imide 1 in 18 % overall yield. The key steps included a highly anti‐selective aldol reaction, the stereoselective iodolactonization of a γ,δ‐unsaturated β‐hydroxyimide, and an intramolecular SN2 reaction of a tertiary alcohol to form intermediate 2.