Über Pterinchemie 80. Mitteilung Die Herstellung von (6RS)Tetra- und (6RS)Pentaacetyl-5,6,7,8-tetrahydro-L-bioplerinen

Preparation of (6RS)Tetra- and (6RS)-Pentaacetyl-5,6,7,8-tetrahydro-L-biopterines Boiling of (6RS) l′-O,2′-O,2-N-triacetyl-5,6,7,8-tetrahydro-L-biopterine in acetic anhydride as described in [2], leads to a mixture of the diastereoisomeric (6R)- and (65)-l′-O,2′-O,2-N-,5,8-pentaacetyl-5,6,7,8-L,-biopterines. One of the diastereoisomers can be obtained as pure crystals. It corresponds to the pentaacetate of the natural (6R)- or (6S).,5,6,7,8-tetrahydro-L-biopterine. For the preparation of the earlier described (6RS)- and (6S)-tetraacetyl-tetrahydro-L-biopterines [2] improved conditions are reported.     

Thermoconversion of Caryophyllene- to Farnesene-Type Sesquiterpenes. Short access to the enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes

Flash-vacuum thermolysis of the four diastereoisomeric 5,6-epoxy-5,6-dihydro-caryophyllenes 1–4 at 500–550°/0.1–0.7 Torr leads to the hitherto unreported enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes ((±)- 5 and (±)- 6 , resp.). In particular, (+)- 5 is formed in 45% yield (ca. 90% ee) and is, thus, an attractive chiral building block for natural-product synthesis.     

(1SR,2SR,3SR,4RS,5RS,6RS,7SR,8RS)‐7,8‐Dichloro­bicyclo­[4.2.0]octa‐2,3,4,5‐tetrayl tetra­acetate

In the title compound, C₁₆H₂₀Cl₂O₈, the bicyclic system contains a central non‐planar cyclo­hexane ring which is fused to a cyclo­butane moiety. The cyclo­hexane ring has a chair conformation and the whole system adopts a syn conformation. The structure provides information on the stereochemical course of the chlorination, photo‐oxidation and hydrox­ylation steps of the reaction.     

(6′RS,8′RS,2E)- und (6′RS,8′SR,2E)-3-Methyl-3-(2y,2′,6′-trimethyl-7′-oxabicyclo[4.3.0]non-9′-en-8′-yl)-2-propenal ([(5RS,8RS)- und (5RS,8SR)-5,8-Epoxy-5,8-dihydro-ionyloinden]acetaldehyd): Synthese und Röntgenstrukturanalyse

Synthesis and X-Ray Structure of (6′RS,8′RS,2E)- and (6′RS,8′SR,2E)-3-Methyl-3-(2′,2′,6′-trimethyl-7′-oxabicyclo[4.3.0]non-9′-en-8′-yl)-2-propenal ([(5RS,8RS)- and (5RS,8SR)-5,8-Epoxy-5,8-dihydro-ionylidene]acetaldehyde) To check our previous spectroscopic assignments of the structures of trans- and cis-substituted furanoid end groups of carotenoid-5,8-epoxides, we now have synthesized the title compounds. An X-ray structure determination of a single crystal of the trans-isomer (±)- -10A is in agreement with the ¹ H-NMR spectroscopic arguments: isomers with Δδ (H? C(7), H? C(8)) = 0.15–0.22 ppm and J > 1.4 for H? C(7) belong to the cis-series; Δδ in trans-compounds is < 0.07 ppm, and H? C(7) appears as a broad singulett.     

Technische Verfahren zur Synthese von Carotinoiden und verwandten Verbindungen aus 6-Oxo-isophoron. VII. Synthese von Rhodoxanthin und (3RS,3RS)-Zeaxanthin aus der C15-Ringkomponente

Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. VII. Synthesis of Rhodoxanthin and (3RS,3RS)-Zeaxanthin from the C₁₅-Ring Component¹ An efficient 7-step synthesis of (3RS,3RS)-zeaxanthin ( 3 ) in 20% overall yield starting from 6-oxo-isophorone ( 7 ) is described. Intermediates are 6,6′-dihydro-rhodoxanthin ( 4 ) and rhodoxanthin ( 1 ), which are now accessible in 4 and 5 steps, and 45 and 25% overall yield, respectively. Novel methods for the simultaneous removal of the hydroxy group and the partial reduction of the triple bond of a monoalkynylated 1,4-dioxo-2-ene system have been developed.     

Enzymatic resolution of methyl (1RS)-N-tBoc-6-hydroxy-3,4-dihydro-1H-isoquinoline-1-carboxylate by Seaprose S

An efficient biocatalytic process has been developed for the resolution of methyl (1RS)-N-tBoc-6-hydroxy-3,4-dihydro-1H-isoquinoline-1-carboxylate rac-1 by means of Seaprose S-mediated enantioselective hydrolysis to afford (1S)-2 and (1R)-1 in 87% and 93% isolated yield, 101% and 96% potency, and ee >99.8% and >99.5%, respectively.