Camphane ethers

Addition of acids, such as acetic, propionic, isobutyric, and isovaleric, produces useful isobomyl esters, the most important of which is isobomyl acetate [125-12-2] (117) (131). Isobornyl acetate possesses a fruity and woody odor and its perfumery use runs into thousands of tonnes per annum. The isobomyl esters of acrylic and methacryUc acids are also useful in preparing acrylic polymers. Similarly, addition of alcohols and glycols to camphene catalyzed by strong acids such as Amberlyst 15 ion-exchange resin produces useful camphane ethers (118) (132). 

Silyl enol ether 139 has also been transformed into D-allose, as shown in Scheme 5. The same methods can be applied to the enantiomeric enol ether derived from camphanate 38, and this allows one to prepare L-allose and its derivatives. Oxidation of 139 with MCPBA in THF (20 °C) led to the product of epoxide acidolysis 147 (69 %) which yielded 148 on heating to 200 °C for 15 min. Addition of 1.1 equiv. of MCPBA converted 148 into lactone 149 which in the presence of MeOH and K2CO3 (20 °C), gave selectively diester 150. Reactions 147... 

To a solution of 3 (8.7 g, 0.06 mol) in anhydrous pyridine (150 mL) lS-camphanic chloric (18.7 g, 0.086 mol) [48] was added and the mixture was left at room temperature. After 48 the solution was poured into ice-water and extracted with CHC13. Combined chlorofor extracts were washed with water, dried (MgS04), and concentrated to dryness. Crude est was dissolved in 40 mL ether and cooled to a — 15°C. The deposited crystals (first fractio 8.96 g) were crystallized four times from the same solvent, 4.5 g of pure 3 mp 102 103.5°C, [a]578 - 29.8° (c 2.02, C6H6). 

Full details of the previously reported (Vol. 6, p. 73) synthesis of the seco-illudane sequiterpenoid hypacrone (346) have been published. An interesting feature of the synthetic route is the use of a directed crossed aldol condensation between the diketone (344) and the trimethylsilyl enol-ether (343) to produce the trans-isomer (345) of hypacrone (346). The absolute configuration of fomannosin (347) has finally been established by X-ray analysis of the camphanate ester derivative (348). Full details of the biosynthesis of fomannosin (347) from [l,2- C2]acetate (c/. Vol. 7, pp. 82, 196) have been published. The labelling pattern and couplings in fomannosin (347) are consistent with a biosyn-... 

As described above, the l-(or 3-) hydroxyl group of myo-inositol has higher reactivity over other equatorial hydroxyls. This tendency was observed in the following examples. Phosphorylation of 155 with diphenyl phosphorochloridate produced the 1,3-diphosphate 156 predominantly in moderate yield together with 1,5-diphosphate 157 (Scheme 3-24).15,55 Benzylation of the triol 155 under PTC conditions led to the 1-benzyl ether 158 in 71% yield (overall yield from the orthoester 95 in three steps). The resultant tetrabenzyl ether 158 was again regioselectively acylated at C-3 with camphanic acid chloride for resolution (Scheme 3-24).42... 

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