Menthol acetate

In the case of lipases and esterases, chiral recognitions are not so strict. Both enantiomers were incorporated to the enzyme to form the substrate-enzyme complex. However, the slow reacting enantiomer lacked the necessary hydrogen-bonding interaction, for example in the hydrolysis of menthol acetate, between the substrate menthol and the enzyme histidine group for the reaction to proceed further (Figure 3(b)).2 3 The explanation was also supported by the observation in the esterification reaction of 1-phenylethanol by lipases.4 Km values of the slow and fast reacting... 

SYNS FEMA No. 2668 MENTHOL, ACETATE (SCI) MENTHYL ACETATE MENTHYL ACETATE racemic P-MENTH-3-YL ESTER-dl-ACETIC ACID... 

Menthol, acetate. See dl-Menthyl acetate Menthol acetic acid. See Menthyl acetate Menthol carboxamide. See N-Ethyl-p-menthane-3-carboxamide... 

Uses ndReactions. The main use for citroneUol is for use in soaps, detergents, and other household products. It is also important as an intermediate in the synthesis of other important fragrance compounds, such as citroneUyl acetate and other esters, citroneUal, hydroxycitroneUal, and menthol. 

Menthol (hRf 15) and menthyl acetate hRt 55) yielded blue chromatogram zones caryophyllene hRf 90) and caryophyllene epoxide hRf 20 — 25) appeared red-violet and thymol hRf 40 — 45) appeared brick red in color. 

Fig. 1 Schematic sketch (A) of the separation of essential oil components (ca. 500 ng of each component) and reflectance scan of the mixture (B). Menthol (1), caryophyllene epoxide (2), thymol (3), menthyl acetate (4), caryophyllene (5), mixture (G).

Menthol forms an acetate, menthyl acetate,. COCHj, a thick... 

Standnikow has prepared several of the esters of menthol by heating magnesium iodo-mentholate with the esters of ethyl alcohol. For example, with ethyl acetate, propionate, and benzoate the corresponding menthyl esters were obtained. These bodies have the following boiling-points —... 

Menthyl Acetate.—This ester, of the formula CHg. CO. OC, H g, is-present in oil of peppermint, its odour being an important characteristic of that oil. It can be prepared by heating menthol with acetic anhydride and sodium acetate. Its characters are as follows —... 

In y-alkoxyfuranones the acetal functionality is ideally suited for the introduction of a chiral auxiliary simultaneously high 71-face selectivity may be obtained due to the relatively rigid structure that is present. With ( + )- or (—(-menthol as auxiliaries it is possible to obtain both (5S)- or (5/ )-y-menthyloxy-2(5//)-furanones in an enantiomerically pure form293. When the auxiliary acts as a bulky substituent, as in the case with the 1-menthyloxy group, the addition of enolates occurs trans to the y-alkoxy substituent. The chiral auxiliary is readily removed by hydrolysis and various optically active lactones, protected amino acids and hydroxy acids are accessible in this way294-29s-400. 

Clive and coworkers have reported a total synthesis of calicheamicinone, the aglycon of the antitumor agent calicheamicin starting from the Diels-Alder reaction of methyl 3-nitro-propenoate with ketene acetal (Eq. 8.32).54 An asymmetric Diels-Alder reaction between ketene acetal presented in Eq. 8.32 and 3-nitropropenoate derived from (-)-8-phenyl-menthol affords the optically pure adduct, which can be converted into either enantiomer of calicheamicinone (Eq. 8.33).55... 

S,3//,4/C6//)-carane-3,4-diol with (l/ )-tra s-chrysanthemic acid is 0.62, and the Rf. value of the corresponding ( l,S )-/ra .v-chrysanthemic acid ester is 0.65 (toluene ethyl acetate = 3 1). However, the /-menthol ester of (1 /. S )-/ra .v-chrysanthemic acid could not easily be separated by silica gel column chromatography to obtain (1 AfWran.v-chrysanthemic acid /-menthol ester. 

Electrochemical oxidation of enol acetates in an undivided cell gives monomeric products in parallel with the reactions of simple alkenes [47, 48]. Thus, in the reaction of menthol enol acetate 23, the a-acetoxyketone product arises from nucleophilic attack of acetate ion on the radical-cation while the enone product... 

In contrast, electrophilic additions to the double bond of acetal 70 (derived from 64 ) gave adduct mixtures 71/72 with regioselectivities opposite to those of reactions 64 + EX — 68 + 69, 72 being the major adducts. Tests were carried out to confirm that adducts 68 + 69 and 71+72 were formed under conditions of kinetic control. Acetal 70 was obtained optically pure via resolution of lactol 73 by medium pressure chromatographic (silica gel) separation of the diastereomeric acetals 74 derived from (-)-menthol. ... 

Figure 11.6 indicates approximate /-values for some of the components in peppermint oil on a BPX-5 column this column selects mainly on the basis of molecular weight and shape. For example p-pinene has the same molecular weight as limonene but has a more compact shape and thus a lower /-value. Menthyl acetate has a higher /-value than menthol because of its higher molecular weight. 

Chiacchio et al. (43,44) investigated the synthesis of isoxazolidinylthymines by the use of various C-functionalized chiral nitrones in order to enforce enantioselec-tion in their cycloaddition reactions with vinyl acetate (Scheme 1.3). They found, as in the work of Merino et al. (40), that asymmetric induction is at best partial with dipoles whose chiral auxiliary does not maintain a fixed geometry and so cannot completely direct the addition to the nitrone. After poor results with menthol ester-and methyl lactate-based nitrones, they were able to prepare and separate isoxazo-lidine 8a and its diastereomer 8b in near quantitative yield using the A-glycosyl... 

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