Epoxygeranyl acetate

Barrero, Oltra and coworkers reported on the use of epoxygeranyl acetate in titanocene-mediated cyclizations and found that the termination of the reaction took place via a /i-hydride elimination after trapping of the radical by the second equivalent of Cp2TiCr [94,95]. This finding together with Takahashi s tandem cyclization [96] (see below) marks the first example of extremely interesting developments in epoxypolyene cyclizations via radicals that are discussed separately in the following section. 

Scheme 19 Dependence of the cyclization of epoxygeranyl acetate on the presence of additives...

Males of neotropical euglossine bees (Apidae), called orchid bees, collect odoriferous substances from flowers of orchids and other plants. The floral scents of these species display relatively simple chemical compositions dominated by one or two major components, mostly terpenoids and aromatic compounds such as cr-pinene, 1,8-cineol, eugenol, -dimethoxybenzene (35), 2,3-epoxygeranyl acetate (36), nerolidol, 4-methoxycinnamaldehyde (37), and benzyl benzoate.113 Since the orchid bees have odor preferences, their collection of fragrances leads to specialized pollination of particular plant species. Male bees absorb the floral volatiles with their tarsal hairs, form species-specific bouquets, and finally accumulate them in their hind tibial pouches. These bouquets have potential roles in courtship displays and marking territories.114 115... 

Finally, Fuse et al. recently proposed the use of EtsB together with 2,6-lutidine hydrochloride or 2,4,6-collidine hydrochloride to improve the capacity of the system for regenerating titanocene(III) from Cp2Ti(Cl)H in the [Ti ]-catalyzed cyclization of 6,7-epoxygeranyl acetate [70]. 

The Cp2TiCl-mediated simple 6-endo cyclization of epoxygeranyl acetate was used by Nakai et al. in the preparation of synthons for building the A and C rings of paclitaxel [105], and a similar cychzation of epoxygeranylace-... 

Removal of the solvent on a rotory evaporator (water bath temperature 60°C) yields 2,3-epoxygeraniol as a slightly coloured oil (about 7.9 g, 87%). The product may be further purified by formation of its acetate followed by vacuum distillation (0.025 mmHg, 104-106°C) to yield 2,3-epoxygeranyl acetate as a colourless liquid containing only traces of its 6,7-isomer. ... 

The method was later extended to the synthesis of a number of meroter-penoids from epoxygeranyl carbonates or acetates in a two-step approach combining titanocene catalysis with Stifle reactions (carbonates) [108,109] or copper-catalyzed allylic substitutions (acetates) [110-112], The cyclizations... 

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