300 JOURNAL OF COSMETIC SCIENCE methyl-2-buten-l-al (Scheme 1). The first step, the Grignard reaction of this aidehyde with isobutylmagnesium bromide, afforded the alcohol 1 in 72% yield. Allyl alchol 1 was transformed via the Claisen rearrangement (orthoacetate modification) into the ester 2 (78% yield), which was reduced with lithium aluminum hydride (yield 89%) to the desired alcohol 3. The E configuration of the double bond formed in the Claisen rearrangement was confirmed by 1H NMR (Jn-4,n-5 = 15.6 Hz) as well as by IR (v = 970 cm -1) spectral data. The (Z) isomer of 3,3,7-trimethyl-4-octen-l-ol (8) was ob- tained by four-step isomerization of (E) alcohol 3. Thus alcohol 3 was transformed into tetrahydropyrane ether 5, which was oxidized with m-chloroperbenzoic acid to ep- oxyether 6. The key step of this isomerization, deoxygenation of epoxy ether, was carried out according to the procedure described by Vedejs and Fuchs (11). Deprotection of .3,R=H d c 4, R = Ac 5, R= THP ••••-/'• OTHP b 1 2 OR 7, R = OTHP 8 ,R=H c l• 9 ,R =Ac a) CI-I3C(OC2H5)3, C2HsCOOH ' 138 ø C b) LiA1H 4 c) AcC1, Py d) PPTS, DHP e) MCPBA, CH2C12 f) 1. (C6Hs)2PLi , THF, 2. CH3I g) PPTS Scheme 1

3,3,7-TRIMETHYL-4-OCTEN-1-OLS 301 ether 7 leads to (Z) alcohol 8. The yield of isomerization based on alcohol 3 was 37%. The (Z) configuration of the double bond was confirmed by •H NMR (Jn-4,H-5 = 12.2 Hz) and IR (712 cm-•). 3-Sila analogues of alcohol 3 as well as alcohol 8 were obtained from 4-methyl-1- pentyne. Ethyl silaester 10 was synthesized in a two-step procedure: hydrosilylation of alkyne with dimethylchlorosilane in the presence of hexachloroplatinic acid as a catalyst (12) followed by the Reformatsky reaction of alkenechlorosilane intermediate with ethyl bromopropionate (Scheme 2). Unfortunately, the product mixture isolated from this synthesis (yield 75%) contained, according to GC, 90% of ester 10, 8% of regioisomer 11, and a small amount of the Z isomer of 10. Separation of this mixture by column chromotography on silica gel impregnated with AgNO 3 (4%) afforded pure (above 97%) ester 10. In the last step of synthesis, ester 10 was reduced with lithium aluminum hydride to alcohol 12 in 84% yield. The 3-sila analogue of alcohol 8 was also obtained from 4-methyl-l-pentyne (Scheme 3). Lithium alkyne was silylated at -78øC with vinyl dimethylchlorosilane, and the result- ing vinylsilane 14 (yield 84%) was oxidized with m-chloroperbenzoic acid to epoxide 15 in 81% yield. Then epoxide was reduced with diisobuthylaluminum hydride (DIBAL) to alkynesilanol 16. The application of lithium aluminum hydride for this reduction gave the mixture of products in which the content of alcohol 16 was 30% only. The secondary ot-silenol was obtained as the second main (20%) component in this mixture. Further reduction of alcohol 16 with DIBAL gave the final (Z)-silenol, 17. More effective + • '/ • /C1 H/Sk'c1 Si •. • Si•'"'CO2C2H• 11 •SiOCO2C2H 5 lO • .j d S••O -• 13 a) H 2 PtCI 6 ß b) BrCH 2 CO 2 C 2 I-Is, Zn, THF c) LiA1H 4 ß d) AcC1, Py Scheme 2