Furanoid and Pyranoid Monoterpenoids

Pyranoid monoterpenoid alkaloids have been reviewed, and halogenated members of this class, (84) and (85), have already been discussed in the halogenated monoterpenoids section. The monoterpenoid ether (245) is reported from Artemisia tridentata-, from reported mass spectral data it may well be identical with the previously reported (and uncited) arthole (Vol. 7, p. 20), the characterization of which is still not published. Loliolide (246) is claimed to be an in vivo carotenoid degradation product in Canscora decussata additional spectral data have been published.  

Treatment of the selenide (19) with unbuffered 30% hydrogen peroxide-THF yields the cis- and trans-linalyl oxides (247) via [2,3] sigmatropic rearrangement. Kossanyi et al. have improved upon the efficiency of Vig s synthesis of the four lilac alcohols (248). The synthesis of the furanoid (249), formed during sulphuric acid-catalysed dimerization of isoprene, is straightforward. The known half- 

Arbuzov, I. S. Andreeva, and Z. G. Isaeva, Bull. Acad. Sci. U.S.S.R., 1976, 25, 1584 Chem. Abs., 1977, 85, 143 311 has the structures of these cyclic sulphites hopelessly in error, presumably because conformations and structural formulae have been confused from poor representations in the paper. 

Reagents i, Me2C=CHCH2CHO ii, NaAIEt2H2 iii, p-TsOH iv, AIjOj-CeHe v, Bu 2AIH, -40°C 

Kotake, K. Inomata, S.-I. Aoyama, and H. Kinoshita, Chem. Letters, 1977, 73. 

A new glycol, elsholtzidiol (293), has been reported from Esholtzia densa, Beuth. 

A variant of the ring-closure reactions for the synthesis of rose oxide (299) has been described by Eschinazi. It consists of oxidising the double bond of citronellyl acetate (296) with performic acid, then thermolysing the fully acetylated compound (297) to yield the diene acetate (298), the corresponding alcohol of 

Ohloff, Fortschr. Chem. Forsch., 1969, 12, 185, gives a summary of the relevant 

Tetrahedron Letters, 1969, 279. E. Demole, P. Enggist, and M. Stoll, Helv. Chim. Acta, 1969, 52, 24. 

From many angles sesquiterpenoids continue to challenge the ingenuity of the organic chemist. The past eighteen months have witnessed many elegant syntheses in which new solutions have been found for the exacting problems of skeletal build-up and stereochemical control. In particular, the use of the intramolecular cyclisation of an olefinic diazoketone, first examined by Stork and Ficini, has been the corner-stone of numerous syntheses. 

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