Phellandral

This aldehyde is identical with the naturally occurring phellandral, an aldehyde found in oil of water fennel. If the nitrosochloride of /3-phellandrene be decomposed by acetic acid, dehydrocuminic aldehyde and carvacrol result. 

The first sets of experiments carried out on the reduction of benzoic acids gave mixtures of dihydro and tetrahydro derivatives. This is hardly surprising in the light of the Van Bekkum study. The first systematic investigation appears to have been carried out on p-lsopropylbenzoic acid (84 Scheme 15), ° for which it was found that reduction by lithium-ammonia at -70 C followed by the addition of ethanol and then ammonium chloride at 5 min intervals furnished a 2 1 mixture of trans- and c/i-1,4-dihydro derivatives (85). In the absence of ammonium chloride the 3,4-dihydro isomer (86) was obtained and this could be reduced further to a 2.5 1 mixture of the tetrahydro derivatives (87) (ammonium chloride quench) and ( )-phellandric acid (88). 

As shown in Figure 19.49, S. litura converted (4/ )-p-menth-l-ene (62) at C-7 position to (47 )-phellandric acid (65) (Miyazawa et al, 1996b). On the other hand, when Cladosporium sp. Ti was cultivated with (+)-limonene (68) as the sole carbon source, it converted 62 to trans-p-menthane-l,2-diol (54) (Mukherjee et al, 1973). 

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