title: Structural characterisation and absolute stereochemistry of some degraded carotenoids from New Zealand honeys

authors: Broom, Susan J.

abstract: The structures and absolute stereochemistries of some degraded carotenoids from New Zealand native honeys were elucidated. 

Determination of the absolute stereochemistry of 3,5,6-trihydroxy-β-ionone was attempted by an enantioselective synthesis. A racemic synthesis was achieved starting from β-ionone. The key steps involved regioselective hydroboration of 3,4-dehydro-β-ionone, followed by molybdenum-mediated stereoselective epoxidation of the resulting homoallylic alcohol. Ring opening of the epoxide afforded the required trihydroxy-ionone. Synthesis of both enantiomers of 3,5,6-trihydroxy-β-ionone via enantio- and regioselective functionalisation of 3,4-dehydro-β-ionone was not achieved. Methods of enantioselective enzyme-mediated kinetic resolution of cyclic homoallylic alcohols were investigated. A satisfactory procedure was not developed. 

The absolute stereochemistry of 3,5,6-trihydroxy-β-ionone was determined by analysis of the diastereoisomeric proton chemical shifts of (S)- and (R)-α-methoxyphenylacetate (MPA) derivatives using the extended Mosher-Trost configurational model. This analysis indicated a 3S,5R,6R absolute configuration, the same configuration as 3,5,6-trihydroxy carotenoids. The natural product was extracted from thyme (Thymus vulgaris) honey using established procedures.

Diethyl ether extracts of kamahi (Weinmannia racemosa) honey were found to contain three diastereoisomers (kamahines) of an unusual degraded carotenoid with a 14 carbon skeleton. After acetylation, one of the isomers was fully characterised by multidimensional ¹H and ¹³C NMR spectroscopy, and single-crystal X-ray crystallography, indicating the parent alcohol was 4,5-dihydro-1',5-dihydroxy-2',4,8',8'-tetramethylspiro[furan-2(3)H,7'[6']oxabicylco[3.2.1]oct[2']ene]-4'-one. Comparison of NMR-derived NOE and coupling constant data of kamahine A and B acetates with kamahine C acetate indicated the parent kamahines were C-4, C-5 epimers.
 
The absolute configurations of the kamahines were determined by NMR and a molecular modeling study (MacroModel) of the diastereoisomeric hemiacetal MPA esters. The results of the determination, coupled with a consideration of crystallographically-determined hemiacetal ester conformations obtained from a search of the Cambridge Structural Database, supported the use of the Mosher-Trost model for determination of the absolute configurations of hemiacetals. Furthermore, this analysis suggested that the Mosher-Trost model should be amended to take into account a torsion angle of +25-50° between the methine proton and the carbonyl of hemiacetal MPA esters. Kamahines A-C were shown to have the absolute configurations 1'R,2R,4R,5S,5'S, 1'R,2R,4S,5S,5'S and 1'R,2R,4R,5R,5'S, respectively. The absolute configurations of kamahines A-C were consistent with an abscisic acid precursor.

text: Structural characterisation and absolute stereochemistry of some degraded carotenoids from New Zealand honeys The structures and absolute stereochemistries of some degraded carotenoids from New Zealand native honeys were elucidated. 

Determination of the absolute stereochemistry of 3,5,6-trihydroxy-β-ionone was attempted by an enantioselective synthesis. A racemic synthesis was achieved starting from β-ionone. The key steps involved regioselective hydroboration of 3,4-dehydro-β-ionone, followed by molybdenum-mediated stereoselective epoxidation of the resulting homoallylic alcohol. Ring opening of the epoxide afforded the required trihydroxy-ionone. Synthesis of both enantiomers of 3,5,6-trihydroxy-β-ionone via enantio- and regioselective functionalisation of 3,4-dehydro-β-ionone was not achieved. Methods of enantioselective enzyme-mediated kinetic resolution of cyclic homoallylic alcohols were investigated. A satisfactory procedure was not developed. 

The absolute stereochemistry of 3,5,6-trihydroxy-β-ionone was determined by analysis of the diastereoisomeric proton chemical shifts of (S)- and (R)-α-methoxyphenylacetate (MPA) derivatives using the extended Mosher-Trost configurational model. This analysis indicated a 3S,5R,6R absolute configuration, the same configuration as 3,5,6-trihydroxy carotenoids. The natural product was extracted from thyme (Thymus vulgaris) honey using established procedures.

Diethyl ether extracts of kamahi (Weinmannia racemosa) honey were found to contain three diastereoisomers (kamahines) of an unusual degraded carotenoid with a 14 carbon skeleton. After acetylation, one of the isomers was fully characterised by multidimensional ¹H and ¹³C NMR spectroscopy, and single-crystal X-ray crystallography, indicating the parent alcohol was 4,5-dihydro-1',5-dihydroxy-2',4,8',8'-tetramethylspiro[furan-2(3)H,7'[6']oxabicylco[3.2.1]oct[2']ene]-4'-one. Comparison of NMR-derived NOE and coupling constant data of kamahine A and B acetates with kamahine C acetate indicated the parent kamahines were C-4, C-5 epimers.
 
The absolute configurations of the kamahines were determined by NMR and a molecular modeling study (MacroModel) of the diastereoisomeric hemiacetal MPA esters. The results of the determination, coupled with a consideration of crystallographically-determined hemiacetal ester conformations obtained from a search of the Cambridge Structural Database, supported the use of the Mosher-Trost model for determination of the absolute configurations of hemiacetals. Furthermore, this analysis suggested that the Mosher-Trost model should be amended to take into account a torsion angle of +25-50° between the methine proton and the carbonyl of hemiacetal MPA esters. Kamahines A-C were shown to have the absolute configurations 1'R,2R,4R,5S,5'S, 1'R,2R,4S,5S,5'S and 1'R,2R,4R,5R,5'S, respectively. The absolute configurations of kamahines A-C were consistent with an abscisic acid precursor.

year: 1998

title: Stratigraphy and reserves of pumiceous sand deposits in Perry's 'Asparagus Block' at Horotiu

authors: Nelson, Campbell S.

abstract: The stratigraphic relationships between the deposits of the Hinuera Formation and the Taupo Pumice Alluvium are described over a 16 ha plot of land known as the 'Asparagus Block' at Horotiu. The Hinuera Formation is exposed at the surface at the southern end of this block, and is overlain by a wedge of Taupo Pumice Alluvium which increases in thickness from 0 to 8 m northwards across the block. Lithofacies in the Hinuera Formation are dominated by trough cross-bedded gravelly sands (lithofacies AI), with common cross-laminated sands (lithofacies B) and massive to horizontally laminated silts (lithofacies D). The pumice content of these deposits is mainly <10%, but in lithofacies B and D can locally reach >70%. Lithofacies in the Taupo Pumice Alluvium are dominated by horizontally to inclined (tabular cross-) bedded slightly gravelly sands and sands (lithofacies G 1/2), with common occurrences of horizontally bedded to massive sandy silts (lithofacies D). The pumice content of these Taupo deposits is high, typically >80%. Cross-sections are presented showing an interpreted subsurface distribution of these lithofacies from south to north through the 'Asparagus Block'. The estimated reserve of extractable pumice sand from the block is of the order of about 400,000 to 450,000 m³.

text: Stratigraphy and reserves of pumiceous sand deposits in Perry's 'Asparagus Block' at Horotiu The stratigraphic relationships between the deposits of the Hinuera Formation and the Taupo Pumice Alluvium are described over a 16 ha plot of land known as the 'Asparagus Block' at Horotiu. The Hinuera Formation is exposed at the surface at the southern end of this block, and is overlain by a wedge of Taupo Pumice Alluvium which increases in thickness from 0 to 8 m northwards across the block. Lithofacies in the Hinuera Formation are dominated by trough cross-bedded gravelly sands (lithofacies AI), with common cross-laminated sands (lithofacies B) and massive to horizontally laminated silts (lithofacies D). The pumice content of these deposits is mainly <10%, but in lithofacies B and D can locally reach >70%. Lithofacies in the Taupo Pumice Alluvium are dominated by horizontally to inclined (tabular cross-) bedded slightly gravelly sands and sands (lithofacies G 1/2), with common occurrences of horizontally bedded to massive sandy silts (lithofacies D). The pumice content of these Taupo deposits is high, typically >80%. Cross-sections are presented showing an interpreted subsurface distribution of these lithofacies from south to north through the 'Asparagus Block'. The estimated reserve of extractable pumice sand from the block is of the order of about 400,000 to 450,000 m³.

year: 1997

title: Tā Pikitia Hei Āwhina Kōrero  Collaborative Drawing and Storying

authors: Kururangi, Aorere Helen Mary

subjects: collaborative drawing and storying

abstract: Creating a Māori medium context for beginning learners of te reo Māori to converse in genuine dialogue, was a real challenge for our mainstream bilingual unit. This study involved six Year 3-5 primary school students working in two groups of three. The bilingual unit is in a contributing school in an urban setting.

The teacher, a second language learner herself, found students seldom initiated any spontaneous Māori dialogue and tended to respond only to questions or formal teacher initiated direction. So the project sought to develop and explore the approach Tā Pikitia hei āwhina kōrero or Collaborative Drawing and Storying, to improve Children's Oral Language Acquisition in Māori, using a socially responsive approach (Glynn, Wearmouth,  Berryman, 2006)
 
This method encouraged students to initiate, respond and share their own learning in a social and interactive community of learners. The method also allowed students the freedom to generate conversations about their own interests, ideas and background experiences without teacher intervention or direction. The only requirement was me kōrero Māori i nga wā katoa (speak Māori all the time). A collaborative picture was created as each group of students quickly illustrated their ideas on a large piece of paper.

 Each student was pre tested and post tested using the Aromatawai Reo A Waha  - Kia Tere Tonu  (Berryman  Langdon, 2001).This test assessed each student's Māori vocabulary knowledge and their ability to speak spontaneously about a familiar item. The daily conversations created by each student group involved Tā Pikitia hei āwhina  kōrero was recorded on tape, then transcribed verbatim each day to assess changes over time. 

 Student ownership of the learning and their positive participation resulted in improved language outcomes. At the end of the ten week period there were encouraging gains in the post test, Aromatawai Reo A Waha - Kīanga or spontaneous phrases students were able to generate. Furthermore an improved ability to focus on an oral task, and improved engagement by the students were unexpected positive outcomes of this easy to implement activity.

text: Tā Pikitia Hei Āwhina Kōrero  Collaborative Drawing and Storying Creating a Māori medium context for beginning learners of te reo Māori to converse in genuine dialogue, was a real challenge for our mainstream bilingual unit. This study involved six Year 3-5 primary school students working in two groups of three. The bilingual unit is in a contributing school in an urban setting.

The teacher, a second language learner herself, found students seldom initiated any spontaneous Māori dialogue and tended to respond only to questions or formal teacher initiated direction. So the project sought to develop and explore the approach Tā Pikitia hei āwhina kōrero or Collaborative Drawing and Storying, to improve Children's Oral Language Acquisition in Māori, using a socially responsive approach (Glynn, Wearmouth,  Berryman, 2006)
 
This method encouraged students to initiate, respond and share their own learning in a social and interactive community of learners. The method also allowed students the freedom to generate conversations about their own interests, ideas and background experiences without teacher intervention or direction. The only requirement was me kōrero Māori i nga wā katoa (speak Māori all the time). A collaborative picture was created as each group of students quickly illustrated their ideas on a large piece of paper.

 Each student was pre tested and post tested using the Aromatawai Reo A Waha  - Kia Tere Tonu  (Berryman  Langdon, 2001).This test assessed each student's Māori vocabulary knowledge and their ability to speak spontaneously about a familiar item. The daily conversations created by each student group involved Tā Pikitia hei āwhina  kōrero was recorded on tape, then transcribed verbatim each day to assess changes over time. 

 Student ownership of the learning and their positive participation resulted in improved language outcomes. At the end of the ten week period there were encouraging gains in the post test, Aromatawai Reo A Waha - Kīanga or spontaneous phrases students were able to generate. Furthermore an improved ability to focus on an oral task, and improved engagement by the students were unexpected positive outcomes of this easy to implement activity.

year: 2008