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COMMUNICATIONS enantiomeric efficiencies of this method are fully comparable to those of the enzymatic procedure. 4) This method can provide highly vcrsatilc cyclohexenone chiral synthons very efficiently. 5 ) The reaction mechanism has been proven to include a suprafacial 1.3-hydrogen migration pathway. E.uprrinzcntal ProcedureTranzforiiiatioii o i 6 c into 5b. To a stirred solution of 6 c (405 mg. 1.0 mmol) in I,?-dichloroetliane (4.6 mL) was added [Rh:(S)-hinap)(cod)]ClO~ (18.6 mg. 19.9 inniol) i n 1 .Z-dichloroethane (0.5 mL) dropwise at room temperature under argon ;ind the niiytiire w'as relluxed for 17 11. The solvent was evaporated. the residue dissolved 111 T H F ( 5 mL). and the resulting solution stirred with nBu,NF ( I 0 M in 7 IfF, 1 0 inl,) at 0 ' C for 5 min. The solution was diluted with ether and washed succeaiwly with water and brine. dried over MgSO,. and concentrated under reduced pressure. The residue was chromatographed on silica gel (EtOAc: hexanc 1.9) to gi%e 5b a s colorless crystals (276 mg, 94.9%) (96.1 % LT). A single recrystallmition from hexane give the optically pure material (99.5 "/ o ee) as colorless prism\. m p 32 C. [r];' = -27.0 ((, = 1.08 in CHCI,).

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To ascertain the ontogeny of CSF sink action on a small hydrophilic solute, we investigated the rate and extent of uptake of [14C]urea by lateral ventricle choroid plexus (CP), cisternal cerebrospinal fluid (CSF), cerebral cortex, and cerebellum in 0.5- to 4-wk-old etherized nephrectomized rats. Five hours after ip injection, radiourea penetrated the entire H2O of tissue and CSF in 1-wk-old brain; moreover, for animals 1-4 wk old there was a marked inverse relationship between age and magnitude of steady-state [14C]urea space in all regions. However, there was lack of progression (with advancing age) in distribution times to steady state, undoubtedly a reflection of the complexity of maturational factors (CSF secretion, barrier permeability, biphasic changes in cerebral blood flow, etc.) that affect solute penetration into central nervous system. Analysis of [14C]urea uptake curves for various regions at different stages of development (1 vs. 2 wk) revealed half times (slow component) that were significantly greater at 1 wk (1.2-1.4 h) than at 2 wk (0.5-0.8 h). Steady-state concentration gradients for tracer urea, plasma to CP to CSF, indicated negligible molecular sieving of urea by CP 1 wk after birth; however, after the 2nd postnatal wk CSF sink action on urea became manifest due to development of CSF secretion and molecular sieving at the blood-CSF and blood-brain barriers.