Leaf alcohols

Revision Problem 1 Leaf alcohol (TM 392) is widespread in plants and has the characteristic smell of green leaves and grass. The cis isomer alone has tlfis smell and is used in perfumery. How would you make it ... 

Synthesis Sondheimer (J. Chem. Soc.. 1950, 877) made leaf alcohol this way. 

Lithium acetyhde also can be prepared directly in hquid ammonia from lithium metal or lithium amide and acetylene (134). In this form, the compound has been used in the preparation of -carotene and vitamin A (135), ethchlorvynol (136), and (7j--3-hexen-l-ol (leaf alcohol) (137). More recent synthetic processes involve preparing the lithium acetyhde in situ. Thus lithium diisopropylamide, prepared from //-butyUithium and the amine in THF at 0°C, is added to an acetylene-saturated solution of a ketosteroid to directly produce an ethynylated steroid (138). 

A very large number of volatile substances have been identified in fresh tea leaf.64 Substances present at the highest levels include the ubiquitous leaf aldehyde, trans-2-hexenal, and leaf alcohol, cis-3-hexenol. Both arise from cis-3-hexenal, which is biosynthesized from linoleic acid in leaf as a result of enzymic splitting.65... 

Dzhavelidze, T. A. Phenolic compounds in various parts of tea shoots. Subtrop Kult 1978 1978 154-155. Hatanaka, A., T. Kajiwara and J. Sekiya. Biosynthesis of leaf alcohol the oxygenative cleavage of linolenic acid to cis-3-hexenal and 11-formyl-cis-9-undecenoic acid from linolenic acid in tea chloroplasts. Symp Chem Nat Prod-22nd- Fukuoka, Japan 1979 657-664. 

Free and esterified, saturated primary alcohols occur widely in nature, e.g., in fruit. Since their odor is relatively weak, their use as components in fragrance compositions is limited. Their use in aroma compositions, especially for fruit flavors, is by far more important (e.g., straight-chain C4-C10 alcohols, isoamyl alcohol). Unsaturated alcohols are most important (e.g., leaf alcohol with its intensely green odor) and may impart characteristic notes to compositions. 

Leaf alcohol is used to obtain natural green top notes in perfumes and flavors. In addition, it is the starting material for the synthesis of 2-/rans-6-cw-nonadien-l-ol and 2-trans-6-cis-nona6 Qn-1 -al. 

Hexenol ( leaf alcohol ) Linolenic acid Soy lipoxygenase + plant hydroperoxide lyase + baker s yeast 4 g kg 5-101 year (also by isolation from plant oils) Addition of baker s yeast to obtain the alcohol without yeast the aldehyde is the major product [60, 66]... 

In contrast, olefinic alcohols have strong odors and are widely used in perfumes, though at relatively low concentrations. Leaf alcohol has a very pleasant leafy, green odor. It is found in many flowers and fruits and is the most important of the olefinic alcohols. Commercial leaf alcohol contains at least 90% of the cis isomer. 

The dominance of the double bond in the ci v-3-hexenyl series of esters, as well as in the alcohol (leaf alcohol) and aldehyde, results in a closely related group of materials in which the other functional groups play only a modifying role in the odor, despite the small size of the C6 chain ... 

Our next target is an allylic alcohol that produces the perfumery compound violet leaf alcohol by a rearrangement step, Two disconnections are possible, but one of them, (a), leads back to a Grignard reagent that can be made by FGI on the violet oil component whose synthesis we described on p. 785. 

The synthesis was best carried out using the alkylmagnesium iodide and the iodide was made from the alcohol via the chloride, violet leaf alcohol precursor synthesis... 

SYNS BLAETTERALKOHOL FEMA No. 2563 P-y-HEXENOL cis-3-HEXEN-l-OL (FCC) LEAF ALCOHOL... 

SYNS CUCUMBER alcohol FEMA No. 2780 NONADIENOL 2-crans-6-cis-NONADlEN-l-OL VIOLET LEAF ALCOHOL... 

---