Antipodal cells

Take the standard Z2-equivariant cell decomposition of with two antipodal cells in each dimension. Divide X °), the set of the vertices of X, into two disjoint sets X ° = AVJB such that every orbit of the Z2-action contains exactly one element from A and one element from B. Let a, b be the 0-skeleton of and map all the points in A to a, and all the points in B to b. Call the edges having one vertex in A and one vertex in B multicolored, and the edges connecting two vertices in A, resp. two vertices in B, A-internal, resp. B-internal. 

Dioxygenases that are exploited at present do not provide general access to antipodal cis-diols and a combined chemoenzymatic strategy is required. While oxidation of bromobenzene (and other mono- and dihalogenated precursors) with TDO expressing cells gives the corresponding (—)-dihydrodiol in excellent... 

Optical compensation for polymers with chiral monomeric units may also occur when the racemic polymer consists of crystallites, each composed only of the rectus chains or only of the sinister polymer chains, and a same amount of optical antipode crystallites is present. This intercrystallite optical compensation211 has been found, for instance, in isotactic poly(propylene sulfide),212 poly ((3 -methy lpropiol ac (one),213 and poly(isopropylethylene oxide),214 where isochiral 2/1 helical chains are included in orthorhombic unit cells according to the space group P2 2 2. ... 

Reaction times were long but yields and e.e. s high. (S)-(+)-a-phenyl-2-pyri-dylmethanol 17 has analgesic and anticonvulsant activities and was a target of this research. However, the antipodal (R)-alcohol was the product from this biotransformation upon prolonged exposure (60 days) to the C. roseus cells. This resulted from a slow selective oxidation of the (S)-alcohol giving a 41 59 mixture of (R)-alcohol 17 (92% e.e.) and ketone 18. 

Both enantiomers of the biologically active Bower s compound, a potent analogue of an insect juvenile hormone [103] (Scheme 18) were prepared using Aspergillus sp. cells in 96% ee. Interestingly, biological tests showed that the (6i )-antipode was about ten times more active than the (6S)-counterpart against the yellow meal worm Tenebrio molitor. 

In this terminology, our definition of projective fullerenes amounts to selection of cell-complex projective-planar 3-valent maps with only 5- and 6-gonal feces. As noted above, P5 — 6 for these maps. Thus, the Petersen graph is die smallest projective fullerene. In general, the projective fullerenes are exactly the antipodal quotients of the centrally symmetric spherical fullerenes. 

The Schreiber synthesis is particularly noteworthy in that the absolute configuration of discodermolide was assigned unambiguously, and through the preparation of numerous analogues the first structure-activity relationship study was possible [35,44], Their synthesis of the unnatural antipode (ent-1) also led to the unexpected discovery that it causes cell cycle arrest in the S-phase [107],... 

There are also many examples that highlight the stereochemical diversity of lignan biosynthesis, as observed in a cell-free extract of Arctium lappa petiole [35], which afforded secoisolariciresinol with the opposite antipode (+) to that formed by Forsythia spp. 

Naloxone, prepared in eight steps from (+)-7-bromodihy-drocodeinone dimethyl ketal (26% overall yield), proved virtually inactive in three test systems (binding, GPI, and neuroblastoma x glioma hybrid cell adenylate cyclase assays) and can thus be used to establish the stereospecific binding of the natural levo isomer.(37) Both antipodes of naloxone are available from a total synthesis of morphinans starting from optically active 1-benzyl-isoquinolines.(128)... 

In any case however, antipodal helices cause countercurrent spectra of the optical rotation, so that the observation of just a single Cotton effect is sufficient to discriminate the antipodes and, in case, enantiomeric solutes. For such an experiment the choice of the infrared spectral range is no longer dictated by the structure period but by the presence of suitable transition moments. The low demand for the chiral solute to be characterized (Korte, 1978) is exemplified by Fig. 4.6-14. In the 20 im wide sample cell an area of 3 mm times 3 mm was filled with approximately 200 pg solution containing circa 0.2 pg of either S-(-) or R-(-i-) Thalidomide (Contergan) in a nematic solvent. In the spectral interval shown, at least three oppositely shaped ACE are found, the pronounced one around 836 cm is related to the 7 (C- H), phenyl-H out-of-plane vibration of the... 

Life as we know it would be impossible without the astonishing characteristics of enzymic catalysis. This catalysis is not only highly efficient, so that reactions may proceed at low temperature and at neutral pH with the speed required by living cells, but it exhibits also a remarkable specificity. Let us cite two typical examples First, the enzyme urease catalyzes the hydrolysis of urea but of no other compound (1). Second, the catalytic action is frequently restricted to one of the antipodes of optically active substrates. Thus, chymotrypsin will catalyze the hydrolysis of acylated L-tyrosinamides, but will not catalyze the reaction of the corresponding derivatives of D-tyrosine (2). 

The resolution of synthetic presqualene and prephytoene alcohols via their etienic acid derivatives has been reported. This work confirmed that the active (-f-)-enantiomers in both series have the same absolute configuration [(li , 2/ , 3/ )]. It has been established, by use of Hn.m.r., that the proton (deuteron) introduced at C-3 during the cyclization of squalene to tetrahymanol by Tetrahymena pyriformis has the 3/8 configuration. Both antipodes of the trimethyldecalol (13) have been shown to be effective inhibitors of cholesterol biosynthesis in rat liver enzyme preparations and cultured mammalian cells. The accumulation of squalene 2,3-oxide and squalene 2,3 22,23-dioxide in the treated systems indicates that inhibition occurs at the cyclization stage. The inhibitor is metabolized to the diol (14). The results of other sterol inhibition... 

Novozyme 435 has also been applied by a Novartis group for the synthesis of optically pure 2,6-di-O-henzoyl-myo-inositol ((-)-99) and its monoacetate (-)-lOO. These intermediates are precursors for the rare and expensive inositol phosphates d-101 and l-101 (Scheme 30) [95], compounds which are essential for a number of physiological processes in differentiated higher cells, e.g., the activation of thrombocytes in the blood clotting process or hormone signal transduction. The key intermediate rac-99 could be prepared in four chemical steps, and the Novo 435-catalyzed asymmetric acetylation afforded monoacetate (-)-lOO besides unconverted inositol derivative (-)-99 with optical purities of >99%, respectively. The subsequent chemical hydrolysis of (-)-lOO quantitatively yielded the antipode of (-)-99, and a phosphorylation. 

Ferguson M, Totri AF, Ward DC et al. In situ hybridization to the Crithidia fosciculata kinetoplast reveals two antipodal sites involved in kinetoplast DNA replication. Cell 1992 70(4) 621-9. 

---