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4.4.16.1.2 Variation 2: Synthesis of Silyl Ketene Acetals and Related Compounds

DOI: 10.1055/sos-SD-004-00346

Kobayashi, S.; Manabe, K.; Ishitani, H.; Matsuo, J.-I.Science of Synthesis, (20024336.

Silyl ketene acetals can be prepared by deprotonation of the parent carboxylic acid esters, followed by silylation of the resulting enolates.[‌257‌] For example, α-disubstituted esters 29 can be converted to the corresponding trimethylsilyl ketene acetals 30 in excellent yields (Scheme 39). Many structural variations can be tolerated, including γ-lactones,[‌258‌,‌259‌] and δ-lactones.[‌36‌] Because trimethylsilyl ketene acetals are more easily hydrolyzed than trialkylsilyl enol ethers, their isolation should be conducted under strictly anhydrous conditions. Ketene acetals of straight-chain esters are more sensitive towards hydrolysis than those of α-disubstituted esters.[‌260‌] The reactivity of tert-butyl(chloro)dimethylsilane toward lithium ester enolates is too low to silylate them without hexamethylphosphoric triamide.[‌260‌] In contrast to trimethylsilyl ketene acetals, tert-butyldimethylsilyl ketene acetals can be purified by aqueous workup procedures,[‌248‌] and the added hexamethylphosphoric triamide can be easily removed from the mixture by simple extraction. Silyl ketene acetals can also be converted to the corresponding lithium enolates by reaction with methyllithium in tetrahydrofuran.[‌259‌]

Meeeee 88 Meeeeeeeeee ee Meeeee Meeee Meeeeeeeeeeee Meeeeee eeee Meeeee[‌888‌]

Me eee eeeeeeeeee ee eeeee eeeeeee eeeeee, eeee M-eeeeeeeeee eeeeee, eee eee eeeeee ee M- eeeeee M-eeeeeeeeee eeeeeee ee eee eeeeeeeee ee eee eeeeee, eee eeeeeeeee ee eee eeeeeeeeee eeeeee, eee eee eeeeeeee eeeeeeeeee. M eeeee eeeeeee eeeeeee ee eee eeeee eeeeee M-eeeeeeeeee ee eeee 88, eeeee eeeeeeeeeeee ee eee α-eeeeee eeeeee M-eeeeeeeeee ee eeee 88 (Meeee 8).[‌888‌,‌888‌] Meeeeeeeee ee eee eeeeeeee ee eeeeeeee ee eeeee ee eeee eeeeeee e eeeeeee ee M- eee M-eeeeeeeee eeeeeeee, eee eeeeee eeeeee 88 eeee M-eeeeeeeeeeeeeeeeee eeeeeeee 88 (Meeeee 88).[‌888‌] Me eee eee eeeeeeeeee eeeeee, eeee-eeeee(eeeeee)eeeeeeeeeeeeee eee e eeeeeee eeeeeeee eeee eeeeeeeeeeeeeeeeeeeee ee eeeeeee M-eeeeeeeee eeeeeeee 88. Meeeeee, eeeeee(eeeeee)eeeeeeeeeeeeee eeeeeeeeeee eeeee ee M-eeeeeeeee eeeeeeee.[‌888‌,‌888‌]

Meeee 8 Meeeee ee eee Meeee Meeeeeeee ee eee Meeeee ee M- ee M-Meeeeeeeee ee Meeee Meeeeeee

Meeee Meeee 88/88 Mee
M8 M8 M8
M M Me 88:88 [‌888‌]
M M Me 88:88 [‌888‌]
M M e-Me 8:88 [‌888‌]
(MM8)8Me M Me 88:8 [‌888‌]
Me Me Me >88:8 [‌888‌]
(MM8)8 Me >88:8 [‌888‌]

MMMM=eeeeeee M-eeeeeeeeeeeeeeeeeeeeeeee.

Meeeee 88 M-Meeeeeeeee ee Meeeeee Meeee Meeeeeee[‌888‌]

Mee eeeeeeeeeeeeeee ee M- ee M-eeeee eeeeee eeeeeee eee ee eeeeeeeeee ee eeeeeeee eee eeeeeee eeeeee.[‌888‌,‌888‌] Me eeeeeee, eeeeeeeeeeeee ee eeeeee ee eeeeeeeeeeeeeee, eeeeeeee ee eeeeeeeeee eeeee ee M-eeeee eeeeee eeeeeee, eeeeeee eeeeeeeeeeeee ee eeeeeeeeeeeeeeeeeeee eeeeeeee/eeeeeeeeeeeeeee eeeee ee M-eeeeeee. Mee eeeeeee, eeeeeeeeeeeee ee eeeeee eeeeeeee (88, M8=Me; M8=Me) eeee eeeeeee eeeeeeeeeeeeeeee ee eeeeeeeeeeeeeee ee 88°M eeeee, eeee eeeeeeeeee eeee eeee-eeeee(eeeeee)eeeeeeeeeeeeee, e 88:8 eeeee ee eee M- eee M-eeeee eeeeee eeeeeee 88 (Meeee 8).[‌888‌] Me e 88% eeeeeeeeeeeeeeeeeeee eeeeeeee/eeeeeeeeeeeeeee eeeeeee, eee eeeee eeeeee eeeeeee 88 eee eeeeeeee ee ee (M/M) 88:88 eeeee. Meeee, ee eeeeeeeeeee ee eee eeeeeeeeeee eee eee eeeeeeeee ee eee M-eeeee eeeeee eeeeeee eee eeee eeeeeeee eeeee e ee-eeeeeee eeeeee, 88% 8,8-eeeeeeee-8,8,8,8-eeeeeeeeee-8(8M)-eeeeeeeeeeee/eeeeeeeeeeeeeee.[‌888‌] Meeeeee, eeeeeeeee ee M-eeeeeeeeeeeeee eeeeee eeeeeee ee eeeeeeeee ee eeee eeeee, eeeeeee eeeeeeeeeeeeeeeeeeee eeeeeeee ee 8,8-eeeeeeee-8,8,8,8-eeeeeeeeee-8(8M)-eeeeeeeeeeee eeee ee eeeeeee eeee eee eeeee eeeeeeee eeeeeee eeeee eeeeeeeee eeeeeeeeee, eeeeeee ee eeeeeeeeeeee. Me eeeee eeee eeeeeeeeeeee, eeee-eeeeeeeeeeeeeeeeee eeeeee eeeeeee eee eeeeeeeeeee eeeeeee ee eee eeeeeeeeeeeeee eeeeee eeeeeee.

Meeee 8 Meeeee ee eee Meeeeee Meeeee eee eee Meee ee eee Meeee Meeeee Meeee ee eee Meeeeee Meeeeeeeeeeeeee ee eee M-Meeeeeeeee ee Meeeee

M8 M8 Meeeeee Meeee (M/M) Mee
Me Me MMM 88:8 [‌888‌]
Me Me MMMM/MMM 88:88 [‌888‌]
Me Me MMM 88:8 [‌888‌]
Me Me MMMM/MMM 8:88 [‌888‌]
e-Me Me MMM 88:8 [‌888‌]
e-Me Me MMMM/MMM 8:88 [‌888‌]
Me e-Me MMM 88:8 [‌888‌]
Me e-Me MMMM/MMM 88:88 [‌888‌]
Me Me MMM 88:88 [‌888‌]
Me Me MMMM/MMM 8:88 [‌888‌]

Mee eeeeeeeeee ee eee eeeeee eeeeee ee eeeeee eeeeeeeee eee M/M eeeee ee eeeee eeeeee eeeeeee. Mee eeeeeee eee eeeeee eeeee, eee eeeeee eee eeeeeeeeeee eee eee M-eeeeeee. Me eee eeeee eeee, eeee eeeee eeeeee eeeeee eeeeee eee eeeeee eeeeeeeeeee eee eee M-eeeeeee (Meeee 8).[‌888‌]

Meeeeeeeeeeeeee, eeee eee eeeeeee eeeeee ee eeeeeeeeeeeeeee eeeee, e eee-eeeeeeee eeeeee eeeeeeeeee eeeee 88 eeeee ee ee ee eeeeee eeeeee eee eeeeeee eee eeeeee ee eeeee eeeeeeeeeee (Meeeee 88). Me eee eeeee eeee, ee eee eeeeeeee ee eeeee eeeeeeeeeee ee eeeeeee eeeeeeeee, eeee ee eeeeeeeeeeeeeeeeeeee eeeeeeee eee 8,8-eeeeeeee-8,8,8,8-eeeeeeeeee-8(8M)-eeeeeeeeeeee, eeeeeeeeeee eeee eeeee eeeeeeee eeee eee eeeeee eeeeee eeeeeeeeeee eee ee eeeeeee eeeeeeeeee eeeee 88.[‌888‌,‌888‌,‌888‌] Meeeeeee, e eeeeeee eeeeeeeeee eeeeeee[‌888‌] ee eeeeeeeeeee eeee eee eeeeeeeeeee eeeeeeeeee eeeeeeeeeee eeeeeeeee eeeeeeeee eeeee eeeeeeee eee eee eeeeeeeee eeeeeeeee ee M- eee M-eeeee eeeeee eeeeeee ee eeeeeeeeeeeeeee eee eeeeeeeeeeeeeee/eeeeeee eeeeeee eeeeeee. M eeeeeeeeeeeee eeeeeeeeeeeee eeeeeeeee eeeee ee ee ee eeeee eeeeeeeeee eeee eeeee eeeeeeee.

Meeeee 88 Meeeeeeeee Meeeee Meeeeee ee eee Meeeeeeeeeeeeee Meeeeeeee ee Meeee Meeeee Meeeeee[‌888‌,‌888‌,‌888‌]

Me eee eeee ee eeeeee eeeeeeeeeeeee,[‌888‌] eeeeeeeeeeeee ee eee eeeeee eeeee eeeeeee eeeeee eeeeee, eee M-eeeee eeeeee eeeeee eeeee eeeeeee eeeeeeeeee ee eee M-eeeeee ee eee eeeeeeee ee eeeeeee eeeeeeee eee eeeeeeeeeeeeeeeeeeee eeeeeeee ee eeeeeeeeeeeeeee.

Mee eeeeeeeeeeeee ee eee eeeeeee eeeeeee eee eeee eeeeeeeee ee M-eee eeeeeeee,[‌888‌] eee eeeeeeeeee ee eee eeeee eeeeeeee eee eeee eeeee ee eeeeeee eeee eeeeeeeee ee eeeeee eeee eeeeeeee.[‌888‌]

Meeeeeeeee eee ee eeeeeeeee eeee eee eeeeeeeeeeeee M-eeeee eeeeee eeeeeeeeeee.[‌88‌,‌888‌,‌888‌] Meeeeeeeee eee eeeeeeeeeeeeee eeee eeeeeee ee eeeeeee eeee eeeeee, eee eeee eee eeeeeeee ee eeee eeeeee M- (eeeeeee eeeeeeeeeeeeeeee, eeeeeeeeeeeeeee)[‌888‌] ee M-eeeeeeee (eeeeeee eeeeeeeeeeeeeeee, eeeeeeeeeeeeeee/eeeeeeeeeeeeeeeeeeee eeeeeeee), eeeeeee ee eeeeee eeeeee (Meeeee 88). Mee eeeeeeeee M-eeeee eeeeee eeeeeeeeeee eee ee eeeeeeee ee ee eeeeeee eeeeee. Meee eeeee ee eeeeeeeee eeee eeeeee eeeeee, eee M-eeeeeeeeeeeeee eeeeee eeeeeee eee ee eeeeeeee eeeeee. Mee eeeeeee, M-eeee-eeeee eeeeeeeeeeeeee (88) eee ee eeeeeeeee eeee (8M)-8-(eeee-eeeeeeeeeeeee)eeee-8-eeee eeeeeeeeeeeeee eeeee (88) ee eeeeeeeeeeeee eeee eeeeeee eeeeeeeeeeeeeeee ee eeeeeeeeeeeeeee, eeeeeeee ee eeeeeeeeee ee eee eeeeeeeee M-eeeeeee. (M)-88 ee eeeeeeee ee eee eeeeeeeeeeeee ee eeeeeee eeeeeeeeeeeeeeee ee eeeeeeeeeeeeeeeeeeee eeeeeeee/eeeeeeeeeeeeeee, eeeeeeee ee eeeeeeeeee ee eee eeeeeeeee M-eeeeeee eeeeeee.

Meeeee 88 Meeeeeeeeeeeeee Meeeeeeee ee Meeeee Meeee Meeeeeeeeee eeee e Meeeeeeee[‌888‌]

Meeee eeeeeeeeeeee eeeee α-eeeeeeeee eee eee eeeeeeee eeeee eeee eeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeee/eeeeeeeeeeeee ee eeee eeeeeeeeeee ee eeee eeeeee eeeeeee ee eeee eeeeee; eeee eeeeeeee eeeee eeee eeee-eeeee eeeeee. Mee M-eeeeeee ee eeeee eeeeee eeeeeee eee eeeeeeee ee eeee eeeee eeeee eeee eeeeeeeeee.[‌888‌] Meeee eeeeeeeeeeee eeeeeeee ee eee α-eeeeeeee eeee eee eeee eeeeeeeee eeee eeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeee. Meeeee eeeeeeeee eeeeee eeeee eeee eeeeeeeeeeeee eeeeeeeeeee eee eeeeeeeeeeeeee ee eeeee M-M-eeeee eeeeee eeeeeee ee eeee eeeeee.[‌888‌] Meeeeeeeee eeeeeee ee eeeee eeeeee α-MM eeeeeee, M-eeeee eeeeeeeeeeeeeeee eeeee eeee eeeeeee eeee eeeeeeeeeeeeee eeeeeeeeeeeeeeeeeeeeeeeee/eeeeeeeeeeeee eeee eeeee eeeeeeeeeeee.[‌888‌]

M eeeeeeeeeeeeeee eeeeeeeee ee eeeee eeeeee eeeeeee eeee α-eeeeeee eeeeee eee eeee eeeeeeeeee.[‌888‌] Meeeeee eee eeeeeeeeeee ee α-eeeeeee eeeeee ee eeeeeeee eeeeeeeeee ee eeeeeeeee eeeeeee eee α-eeeeeee eee eeeeeeee eeeeeee, M-eeeee eeeeee eeeeeee eee eeeeeeee eeeeee.[‌888‌] Mee M-eeeee eeeeee eeeeee 88 ee eeee-eeeeeeeeeeeeeeeeee eeeeeeeee α-eeeeeee eeeee 88 ee eeeeeeeeeee eeeeee ee eee eeeeeeee eeeeee eeeeee ee eee eeeeeee eeeeeee eeeeeeeee eeeee e eeeeeeee eeee, eeeeeee 8,8,8,8-eeeeeeeeeeeeeeeeeeeee (MMMM) (Meeeee 88). Me eee eeeee eeee, eee eeeeeeeeeeeee M-eeeee eeeeee eeeeee 88 ee eeeeeeeeeee eeeeee ee eee eeeeeeee eeeeee ee eee eeeeeee, eeeee ee eeeeeeeee eeeee e eeee eeeeee eeee, eeeeeee 8,8,8,8,8,8-eeeeeeeeeeeeeeeeeeee (MeMMMM) ee eeeeeeeeeeeeeee/eeeeeeeeeeeeeeeeeeee eeeeeeee.

Meeeee 88 Meeeeeeee Meeeeeeee ee M- eee M-Meeee Meeeee Meeeeee eeee ee α-Meeeeee Meeee[‌888‌]

Me eee eeee ee eeeee α-eeeeeeeeeeeeeeeeeeeee, M-eeeee eeeeee eeeeeee eee eeeeee eeeee eeeeeee eeeeeeeeee (eeeeeee eeeeeeeeeeeeeeee, eeeeeeeeeeeeeee, 88°M), eee M-eeeee eeeeee eeeeeee eee eeeeee eeeee eeeeeeeeeeeee eeeeeeeeee (eeeeeee eeeeeeeeeeeeeeee, eeeeeeeeeeeeeeeeeeee eeeeeeee/eeeeeeeeeeeeeee, 88°M).[‌888‌]

Meeeeeee eeeeee eee eeeeeeeee ee eeeeeee eeeeeeeeeeeeeeee/eeeeeeeeeeeeeeeeeeeee, eee eeee M- eee M-eeeeeeeee eeeeeeee eee eeeeeeee.[‌888‌]

Meeeee eee(eeeeeeeeeeeee)eeeeeee 88 eee ee eeeeeeee ee eee eeeeeee.[‌888‌] Mee ee ee eee eeeeeeee ee α-eeeeeeeee eeeeeeeeeeeeee eeeeeeeeeeee eeee eeeeeeeeeeeeeeeeeeeee, eee eee eeeee, eeeeee, eeeeee ee ee eee eeeeeeee ee eee eeeeeeee ee eeeeeeeeee eeeee 88 eeee eeeeeeeeeeeeeeeeeeeee (Meeeee 88). Meeeee eee eeeeeeeee eeeee eeee eeeeeeee ee M- eee M-eeeeeeeee eeeeeeee.

Meeeee 88 Meeeeeeeeee ee Meeeee Mee(eeeeeeeeeeeee) Meeeeee eeee Meeeeeeeee Meeee[‌888‌]

Meeeeeeeeeee Meeeeeeeee

Meeeeeeeeee ee Meeee Meeeee Meeeeee 88 (M8=M) eeee Meeeee 88 (M8=M); Meeeeee Meeeeeeee:[‌888‌]

Me e eeeeee (88°M) eeee ee MMM [eeeeeeee eeee eMe8MM (8.8eee) eee MeMe (8.8eee) ee MMM (88eM)] eee eeeee eee eeeee 88 (M8=M; 8.8eee) eeee 8eee. Meeee eee eeeeeee eee eeeeeee eee e eeeeeee 88eee ee 88°M, ee eeeeee ee MMMMe (8.88eeee) eee eeeee eeee 8eee, eee eee eeeeeee eee eeeeeee ee eeee ee ee. Meeee eeeeeeee eee 88eee, eee eeeeeee eee eeeeeeee eeeee eeeeeee eeeeeee e Meeeee eee, eee eee eeeeeeee eee eeeeeeeeeeee ee eeeee. Mee eeeeeee eee eeeee ee ee Me8M, eee eeeeeeeeee eee eeeeeeeeeeeee eeee eeeeeeee. Meeeeeeeeeee ee eee eeeeeee eeeee eeeeeee eeeeeeee eeee eee eeeeee eeeeee 88 (M8=M); eeeee: ee. 88%.

Meeeeeeeeee ee Meeee Meeeee Meeeeee 88 (M8M) eeee Meeeee 88 (M8M); Meeeeee Meeeeeeee:[‌888‌]

Me e eeee ee MMM ee MMM eee eeeee eee eeeee 88 (M8M; 8.8eee) eeee 8eee ee 8°M. Meeee eee eeeeeee eee eeeeeee eee eeeeeee 88eee, ee eeeeee ee MMMMe (8.88eee) eee eeeee eeee 8eee, eee eee eeeeeee eee eeeeeee ee eeee ee ee. Meeeeeeee ee eeeeeeeee eeeee eeeeeeee ee eeeeeeeeeeee eeee eee eeeeeee eeeeee eeeeee; eeeee: ee. 88%.

Meeeeeeee[(8-eeeeeeeeeeee)eee]eeeeee (88):[‌888‌]

M eeeeeee ee eeeeee eeeeeee (88; 8.8e, 88eeee) eee MMMMe (88eM, 888eeee) eee eeeee eeee 88eee ee e eee-eeeeee (88°M) eeee ee MMM (88eeee, eeeeeeee eeee MeMe ee eeeeeee eee eMe8MM) ee MMM (88eM). Meeeeeee eee eeeeeeeee ee 88°M eee 88eee, eee eeee eee eeeeeee eeee eee eeeeeee eee eee eeeeeee eee eeeeeee ee eeee ee ee. Mee eeeeeee eee eeee eeeeeeeeeeee ee eeeee, eee eee eeeeeee eee eeeeeeeee eeee eeeeeee. Mee eeeeeee eeeeeee eee eeeeeeee eee eeeeeeeeeeee, eee eee eeeee eeeeeee eee eeeeeeeee eeeee eeeeeee eeeeeeee (ee 8888°M/8.8Meee) ee eeee eee eeeeee eeeeee 88; eeeee: 8.8e (88%).

eeee-Meeee[(8-eeeeeeeeeee)eee]eeeeeeeeeeeeee (88); Meeeeee Meeeeeeee:[‌8‌]

8.8M MeMe ee eeeeeee (88eeee) eee eeeeeee eeeeeeee eeee eMe8MM (88eeee) eeee eeeeeeee ee 8°M. Mee eee-eeee eeeeeee eee eeee ee 8°M eee 88eee, eee eeee eee eeeeeee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeeee MMM eee eeeeeeeee ee MMM (88eM), eee eeee eeeeee ee 88°M. MeMMe (88eeee) eee eeeee eeeeeeee, eeeeeeee ee e eeee ee e-MeMe8MeMe (88eeee) ee eeeeeee (88eM). Mee eeeeeee eeeeeee eee eeeeeee ee eeee ee ee eeeeeeeee. Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee, eee eee eeeeeee eee eeeeeeeeeee eeeeeee eeeeeee (888eM) eee eee. MeMMM8 (88eM). Mee eeeeeee eeeeeee eee eeeeee eeee M8M eee eeeee, eee eeeee. Meeeeeeeeeeee eee eeeeeeeeeeee (Meeeeeeee) eeee 88; eeeee: 8.8e (88%); ee 888888°M/88Meee.

(8M)-8-(eeee-Meeeeeeeeeeee)eeee-8-eeee Meeeeeeeeeeeee Meeee [(M)-88]; Meeeeee Meeeeeeee:[‌88‌]

Me e eeee ee MMM (8.8eeee) ee MMM (8eM) ee 88°M, M-eeee-eeeee eeeeeeeeeeeeee (88; 8eeee) eee eeeee eeeeeeee eeeee M8 eeee eeeeeeee. Meeee 88eee, MMMMe (8.8eeee) eee eeeee, eeee eee eeeeeee eee eeeeee ee ee, eeeeeee eeee eeeeeee eee eeeeeeee eeee eM 8 eeeeeeeee eeeeee. Mee eeeeee eeee eeeeeeeee, eee eee eeeeeee eeeee eee eeeeee eeeee eeee eM 8 eeeeeeeee eeeeee eee eeeee (Me8MM8). Mee eeeeeee eee eeeeeeeeee eeeee eeeeeee eeeeeeee ee eeee (M)-88 eee (M)-88 ee e 88:88 eeeeeee.

(8M)-8-(eeee-Meeeeeeeeeeee)eeee-8-eeee Meeeeeeeeeeeee Meeee [(M)-88]; Meeeeee Meeeeeeee:[‌88‌]

Me e eeee ee MMM (8.8eeee) ee 88% MMMM/MMM eeeeeee (8eM) ee 88°M, M-eeee-eeeee eeeeeeeeeeeeee (88; 8eeee) eee eeeee eeeeeeee eeeee M8 eeee eeeeeeee. Meeee 88eee, MMMMe (8.8eeee) eee eeeee. Mee eeeeeee eee eeeeee ee ee, eeeeeee eeee eeeeeee, eee eeeeeeee eee eeeeee ee ee eeeeeeeee eeeee. (M)-88 eee (M)-88 eeee eeeeeeee ee e 8:88 eeeeeee.

Meeeee Mee(eeeeeeeeeeeeee) Meeeeee 88 eeee eee Meeeeeee ee Meeeeeeeee Meeee 88; Meeeeee Meeeeeeee:[‌888‌]

Me e eeeeee (8°M) eeee ee MMM (8.8eee) ee MMM (88eM), e eeee ee eee eeeeeeeeee eeee (88; 8.88eee) ee MMM (88eM) eee eeeee, eee eee eeeeeee eee eeeeeee eee 88eee. Me eeeeee ee MMMMe (8.88eee) eee eeeee eeeeeeee eeee 8eee, eee eee eeeeeee eee eeeeeee ee eeee ee ee eeee 88eee. Mee eeeeeee eee eeeeeeee eeeee eeeee, eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeee eeee eee Me8M (88eM) eee eee eeeeeee eee eeeeeeeeee. Mee Me8M eee eeeeeee eee eee eeeeeee eee eeeeeeeee eeeee eeeeeee eeeeeeee ee eeee eee eeeeee eee(eeeeeeeeeeeeee) eeeeeee 88; eeeee: ee. 8888%.

References