Trouble with dynamic SQL: Unclosed quotation mark before the character string

PROBLEM:  Receive error message:
Server: Msg 105, Level 15, State 1, Line 128
Unclosed quotation mark before the character string 'Un
 into NewTable FROM (select tbl_ecom_productdescriptor_idvaluepairs.product, tlkp_ecom_productdescriptor.dscname, tbl_ecom_productdescriptor_idvaluepairs.dscval from tbl_ecom_productdescriptor_idvaluepairs inner join tlkp_ecom_productdescriptor on tbl_ecom_productdescriptor_idvaluepairs.dscid = tlkp_ecom_productdescriptor.dscid) a
GROUP ...
Server: Msg 170, Level 15, State 1, Line 128
Line 128: Incorrect syntax near 'Un
 into NewTable FROM (select tbl_ecom_productdescriptor_idvaluepairs.product, tlkp_ecom_productdescriptor.dscname, tbl_ecom_pr'.
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I am running the following dynamic sql:
declare
        @table       as varchar(500),
        @onrows      as varchar(128),
        @onrowsalias as sysname ,
        @oncols      as varchar(128),
        @sumcol      as sysname

        set @table=
                '(select tbl_ecom_productdescriptor_idvaluepairs.product, tlkp_ecom_productdescriptor.dscname, tbl_ecom_productdescriptor_idvaluepairs.dscval ' +
                'from tbl_ecom_productdescriptor_idvaluepairs inner join '+
                'tlkp_ecom_productdescriptor on tbl_ecom_productdescriptor_idvaluepairs.dscid = tlkp_ecom_productdescriptor.dscid) a '                
        set @onrows ='product'
        set @onrowsalias= null;
        set @oncols='dscname'
        set @sumcol='dscval'

declare
        @sql as varchar(8000),
        @newline as char(1)

        set @newline = char(10)

        -- step 1: beginning of sql string
        set @sql =
                'select' + @newline +
                '  ' + @onrows +
                case
                        when @onrowsalias is not null then ' as ' + @onrowsalias
                        else ''
                end

        create table #keys(keyvalue nvarchar(100) not null primary key)

--declare  @keys table(keyvalue varchar(100) not null primary key)
declare @keyssql as varchar(1000)
        set @keyssql =
                'insert into #keys ' +
                'select distinct cast(' + @oncols + ' as nvarchar(100)) ' +
                'from ' + @table
exec (@keyssql)

declare @key as nvarchar(100)
        select @key = min(keyvalue) from #keys

        while @key is not null
                begin
                        set @sql = @sql + ',' + @newline +
                        '  max(case cast(' + @oncols +
                                     ' as nvarchar(100))' + @newline +
                        '        when N''' + @key +
                           ''' then ' + case
                                                when @sumcol is null then '1'
                                                else @sumcol
                                        end + @newline +
                        '        else null' + @newline +
                        '      end) as ' + @key
                       
                        select @key = min(keyvalue) from #keys
                        where keyvalue > @key
                end


SET @sql = @sql         + @NEWLINE +
  ' into NewTable FROM ' + @table      + @NEWLINE +
  'GROUP BY ' + @onrows + @NEWLINE +
  'ORDER BY ' + @onrows
--         set @sql = @sql         + @newline +
--                 'from ' + @table      + @newline +
--                 'group by ' + @onrows + @newline +
--                 'order by ' + @onrows

-- for debugging...this information will print into the messages section
-- of query analyzer...prints information to the messages window at the
-- bottom of the screen...
print @sql  + @newline
exec (@sql)