Synthetic studies on pterin glycosides: the first synthesis of 2′-O-(α-d-glucopyranosyl)biopterin

L-Rhamnose was led, in a 14-step-sequence, to N2-(N,N-dimethylaminomethylene)-1′-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (23), an appropriately protected precursor for 2′-O-glycosylation, while 4,6-di-O-acetyl-2,3-di-O-(4-methoxybenzyl)-α-d-glucopyranosyl bromide (32), a novel glycosyl donor, was efficiently prepared from d-glucose in 8 steps. The first synthesis of 2′-O-(α-d-glucopyranosyl)biopterin (2a) was achieved by treatment of the key intermediate 23 with 32 in the presence of silver triflate and tetramethylurea, followed by successive removal of the protecting groups

An Efficient Synthesis of Antibiotic SF-2312 (3-Dihydroxyphosphoryl-1,5-dihydroxy-2-pyrrolidone)

N-Benzyloxy-2-(diethoxyphosphoryl)pent-4-enamide (6) was prepared from ethyl diethoxyphosphorylacetate in a 3-step sequence. Oxidative cleavage of the terminal olefin of 6 with osmium tetroxide and sodium periodate afforded 1-benzyloxy-3-diethoxyphosphoryl-5-hydroxy-2-pyrrolidone (7). The first synthesis of racemic SF-2312 was achieved by treatment of 7 with trimethylsilyl bromide, followed by hydrogenolysis

First Synthesis of Asperopterin A, an Isoxanthopterin Glycoside from Aspergillus Oryzae

The key precursor, N-2-(N,N -dimethylaminomethylene)-6-hydroxymethyl-8-methyl-3-[2-(4-nitrophenyl)ethyl]-7-xanthopterin (16) was efficiently prepared from 2,5-diamino-6-methylamino-3H-pyrimidin-4-one (5) and ethyl 3-(tert-butyldimethylsilyloxy)-2-oxopropionate (12), followed by the protection of the pteridine ring. Glycosylation of 16 with 1-O-acetyl-2,3,5-tri-O-benzoyl-beta-D-ribofuranose (18) in the presence of tin(IV) chloride yielded the corresponding beta-D-ribofuranoside. Successive removal of the protecting groups of the resulting D-ribofuranoside provided asperopterin A (4b)

PENGARUH PEMBELAJARAN AKTIF DENGAN METODE PEER LESSONS TERHADAP HASIL BELAJAR SISWA PADA STANDAR KOMPETENSI MENJELASKAN DASAR-DASAR SINYAL VIDEO DI SMK NEGERI 1 MADIUN

Abstrak Penelitian ini bertujuan untuk: (1) Mengetahui perbedaan hasil belajar siswa yang menggunakan pembelajaran aktif dengan metode peer lessons dengan hasil belajar siswa yang menggunakan pembelajaran ceramah. (2) Mengetahui respon siswa terhadap proses pembelajaran aktif dengan metode peer lessons. Metode penelitian yang digunakan adalah quasi experiment dengan rancangan penelitian yang digunakan yaitu “Nonequivalen Control Design”. Populasi dalam penelitian ini adalah siswa kelas XI TAV SMK Negeri 1 Madiun. Di ambil sampel sebanyak 2 kelas dengan kelas XI TAV-1 sebagai kelas eksperimen dan XI TAV-3 sebagai kelas kontrol. Sedangkan untuk mengetahui perbedaan hasil belajarnya digunakan teknik analisis data uji-t. Hasil penelitian menunjukkan bahwa: (1) Hasil belajar siswa yang menggunakan pembelajaran aktif dengan metode peer lessons lebih tinggi dibandingkan dengan hasil belajar siswa yang menggunakan pembelajaran ceramah dengan rata-rata hasil belajar sebesar 79,2857 (eksperimen) dan 67,3810 (kontrol); (2) Hasil respon siswa terhadap keseluruhan aspek pada lembar angket respon siswa dapat disimpulkan bahwa proses pembelajaran dengan menggunakan pembelajaran aktif dengan metode peer lessons dikategorikan sangat baik dengan rata-rata hasil rating 84,72%. Hal ini menunjukkan bahwa pembelajaran aktif dengan metode peer lessons layak digunakan pada proses kegiatan belajar mengajar di SMK Negeri 1 Madiun. Kata kunci :  Pembelajaran aktif dengan metode peer lessons, Pembelajaran ceramah, Hasil belajar siswa. Abstract This study aims to: (1) Determine the difference in student learning outcomes using active learning with the peer lessons with the use of student learning outcomes lecture lesson. (2) Knowing the students' response to the learning process actively with the peer lessons. The research method used was quasi experiment with research design used is "Nonequivalen Control Design". The population in this study was a class XI student of SMK Negeri 1 Madiun TAV. Sample taken 2 classes with class XI TAV-1 as experimental class XI and TAV-3 as a control class. While to know the differences in the results of their study used data analysis techniques t-test. The results showed that: (1) learning outcomes of students who use active learning lessons with the peer is higher than the results of student learning using learning lecture with an average of 79.2857 learning outcomes (experiments) and 67.3810 (control), (2) the students 'response to all aspects of the students' responses on the questionnaire sheet can be concluded that the process of learning to use active learning methods categorized peer lessons very well with average rating 84.72% yield. This shows that active learning lessons worthy peer method used in the process of learning and teaching in SMK Negeri 1 Madiun. Keywords :  Active learning with the peer lessons, learning lectures, student learning outcomes.

First Synthesis of a Representative, Natural Pterin Glycoside: 2’-O-(α-D-Glucopyranosyl)biopterin

Glycosylation of N(2)-(N,N-dimethylaminomethylene)-1’-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl) ethyl]biopterin (14) with the novel donor 4,6-di-O-acetyl-2,3-di-O-(4-methoxybenzyl)-α-D-glucopyranosyl bromide (19) in the presence of silver triflate and tetramethylurea predominantly afforded the corresponding α-D-glucopyranoside (20a), from which 2’-O-(α-D-glucopyranosyl)biopterin (1) was obtained by the successive removal of the protecting groups

An Efficient, One-Pot Synthesis of Fosfomycin Dialkyl Esters from (R)-2-Tosyloxypropanal

(R)-2-Tosyloxypropanal (4) was prepared from D-mannitol in a 7-step sequence (51% overall yield). Addition of dialkyl phosphonates to 4 in the presence of titanium isopropoxide and the subsequent treatment with DBU stereoselectively afforded, in one-pot, fosfomycin dimethyl (5a) and dibenzyl (5b) esters both in 58% isolated yield

First Synthesis of a Natural Isoxanthopterin Glycoside, Asperopterin-A

The key precursor, N-2-(N,N-dimethylaminomethylene)-6-hydroxymethy1-8-methyl-3[2-(4-nitrophenypethyl]-7-xanthopterin (9) was efficiently prepared from 2,5-diamino-6-methylam1no-3H-pyrimidin-4-one (3) and ethyl 3-(tert-butyldimethylsilyloxy)-2-oxopropionate (11). The first synthesis of asperopterin-A (2b) was achieved by treatment of 9 with 1-O-acetyl-2,3,5-tri-O-benzoy1-beta-D-ribofuranose (15) in the presence of tin(IV) chloride, followed by removal of the protecting groups

First Synthesis of Biopterin α-D-Glucoside

A novel glycosyl donor, 4,6-di-O-acetyl-2,3-di-O-(4-methoxy-benzyl)-α-D-glucopyranosy bromide (15) was efficiently prepared from D-glucose in 8 steps. The first synthesis of 2’-O-(α-D-glucopyranosyl)biopterin (2) was achieved by treatment of the key precursor, N(2)-(N,N-dimethylamino- methylene)-1’-O-(4-methoxybenzyl)-3-[2-(4-nitrophenyl)ethyl]biopterin (6) with 15 in the presence of silver triflate and tetramethylurea, followed by removal of the protecting groups

Improved syntheses of D-ribo- and 2-deoxy-D-ribofuranose phospho sugars from methyl β-D-ribopyranoside

Methyl 4-deoxy-4-dimethoxyphosphinoyl-2,3-O-isopropylidene-beta-D-ribopyranoside (12a) and methyl 2,4-dideoxy-4-dimethoxyphosphinoyl-beta-D-erythro-pentopyranoside (20) were efficiently prepared respectively from methyl 2,3-O-isopropylidene-beta-D-ribopyranoside (7a) and its 3,4-O-isopropylidene isomer (7b) in appreciably improved total yields compared with those via previously reported routes. Compounds (12a, 20) were led to D-ribofuranose and 2-deoxy-D-ribofuranose phospho sugars (4, 5)